diff --git a/.gitignore b/.gitignore
index 6f83e12..36dcc72 100644
--- a/.gitignore
+++ b/.gitignore
@@ -28,6 +28,9 @@ var/
 .eggs/
 .pytest_cache/
 
+# source dirs have to be explicitly added
+src/
+
 # PyInstaller
 #  Usually these files are written by a python script from a template
 #  before PyInstaller builds the exe, so as to inject date/other infos into it.
diff --git a/Makefile b/Makefile
index 6d79625..9f68e6e 100644
--- a/Makefile
+++ b/Makefile
@@ -31,18 +31,22 @@ BUILD_LOG_DIR = "test_build_logs/"
 BUILD_LOG_FILE := $(shell date +"$(BUILD_LOG_DIR)%Y%m%dt%H%M%S%N.log")
 
 
-build/.install.make_marker: setup.py build/envs.txt
-	$(PYTHON36) -m pip install --upgrade --quiet \
-		pip setuptools wheel twine \
-		flake8 mypy typing-extensions \
-		rst2html5 \
-		pytest pytest-cov \
-		ipython pudb \
-		pathlib2 click;
+build/.install.make_marker: setup.py build/envs.txt requirements*.txt
+	$(PYTHON37) -m pip install --upgrade --quiet $$(cat requirements.txt);
+	$(PYTHON36) -m pip install --upgrade --quiet $$(cat requirements.txt);
+	$(PYTHON27) -m pip install --upgrade --quiet $$(cat requirements.txt);
 
-	$(PYTHON37) -m pip install --upgrade --quiet pip setuptools wheel;
-	$(PYTHON36) -m pip install --upgrade --quiet pip setuptools wheel;
-	$(PYTHON27) -m pip install --upgrade --quiet pip setuptools wheel;
+	$(PYTHON37) -m pip install --upgrade \
+		$$(cat requirements-test.txt) \
+		$$(cat requirements-dev.txt);
+
+	# NOTE (mb 2018-08-23): The linter has an issue running with
+	# 	python 3.7 because some code in pycodestyle=2.3.1
+	#	but we have to wait for a flake8 update because
+	#	reasons... https://github.com/PyCQA/pycodestyle/issues/728
+	@mkdir -p lib/
+	$(PYTHON37) -m pip install --src lib/ \
+		-e "git+https://gitlab.com/pycqa/flake8@master#egg=flake8";
 
 	@mkdir -p build/
 	@touch build/.install.make_marker
@@ -54,28 +58,22 @@ clean:
 	rm -f build/.install.make_marker
 
 
-# NOTE (mb 2018-08-23): The linter has an issue running with
-# 	python 3.7 because some code in pycodestyle=2.3.1
-#	but we have to wait for a flake8 update because
-#	reasons... https://github.com/PyCQA/pycodestyle/issues/728
-
-
 lint: build/.install.make_marker
 	@echo -n "lint.."
-	@$(PYTHON36) -m flake8 src/pycalver/
+	@$(PYENV37)/bin/flake8 src/pycalver/
 	@echo "ok"
 
 
 mypy: build/.install.make_marker
 	@echo -n "mypy.."
-	@MYPYPATH=stubs/ $(PYTHON36) -m mypy \
+	@MYPYPATH=stubs/ $(PYTHON37) -m mypy \
 		src/pycalver/
 	@echo "ok"
 
 
 test: build/.install.make_marker
 	@PYTHONPATH=src/:$$PYTHONPATH \
-		$(PYTHON36) -m pytest \
+		$(PYTHON37) -m pytest \
 		--cov-report html \
 		--cov=pycalver \
 		test/
@@ -83,7 +81,7 @@ test: build/.install.make_marker
 
 devtest: build/.install.make_marker
 	PYTHONPATH=src/:$$PYTHONPATH \
-		$(PYTHON36) -m pytest -v \
+		$(PYTHON37) -m pytest -v \
 		--cov-report term \
 		--cov=pycalver \
 		--capture=no \
@@ -107,7 +105,7 @@ build/README.html: build/.install.make_marker README.rst CHANGELOG.rst
 	@cat README.rst > build/.full_readme.rst
 	@echo "\n" >> build/.full_readme.rst
 	@cat CHANGELOG.rst >> build/.full_readme.rst
-	@$(PYENV36)/bin/rst2html5 --strict \
+	@$(PYENV37)/bin/rst2html5 --strict \
 		build/.full_readme.rst > build/README.html.tmp
 	@mv build/README.html.tmp build/README.html
 	@echo "updated build/README.html"
@@ -123,17 +121,18 @@ build/.src_files.txt: setup.py build/envs.txt src/pycalver/*.py
 
 
 rm_site_packages:
-	rm -rf $(PYENV36)/lib/python3.6/site-packages/pycalver/
-	rm -rf $(PYENV36)/lib/python3.6/site-packages/pycalver*.dist-info/
-	rm -rf $(PYENV36)/lib/python3.6/site-packages/pycalver*.egg-info/
-	rm -f $(PYENV36)/lib/python3.6/site-packages/pycalver*.egg
+	# whackamole
+	rm -rf $(PYENV37)/lib/python3.6/site-packages/pycalver/
+	rm -rf $(PYENV37)/lib/python3.6/site-packages/pycalver*.dist-info/
+	rm -rf $(PYENV37)/lib/python3.6/site-packages/pycalver*.egg-info/
+	rm -f $(PYENV37)/lib/python3.6/site-packages/pycalver*.egg
 
 
 build/.local_install.make_marker: build/.src_files.txt rm_site_packages
 	@echo "installing pycalver.."
-	@$(PYTHON36) setup.py install --no-compile --verbose
+	@$(PYTHON37) setup.py install --no-compile --verbose
 	@mkdir -p build/
-	@$(PYTHON36) -c "import pycalver"
+	@$(PYTHON37) -c "import pycalver"
 	@echo "install completed for pycalver"
 	@touch build/.local_install.make_marker
 
@@ -142,13 +141,13 @@ build: build/.local_install.make_marker
 	@mkdir -p $(BUILD_LOG_DIR)
 	@echo "writing full build log to $(BUILD_LOG_FILE)"
 	@echo "building pycalver.."
-	@$(PYTHON36) setup.py bdist_wheel --python-tag=py2.py3 >> $(BUILD_LOG_FILE)
+	@$(PYTHON37) setup.py bdist_wheel --python-tag=py2.py3 >> $(BUILD_LOG_FILE)
 	@echo "build completed for pycalver"
 
 
 upload: build/.install.make_marker build/README.html
-	$(PYTHON36) setup.py bdist_wheel --python-tag=py2.py3
-	$(PYENV36)/bin/twine upload $(BDIST_WHEEL_PYCALVER)
+	$(PYTHON37) setup.py bdist_wheel --python-tag=py2.py3
+	$(PYENV37)/bin/twine upload $(BDIST_WHEEL_PYCALVER)
 
 
 setup_conda_envs: build/.setup_conda_envs.make_marker
@@ -156,4 +155,4 @@ setup_conda_envs: build/.setup_conda_envs.make_marker
 install: build/.install.make_marker
 
 run_main:
-	PYTHONPATH=src/:$$PYTHONPATH $(PYTHON36) -m pycalver --help
+	PYTHONPATH=src/:$$PYTHONPATH $(PYTHON37) -m pycalver --help
diff --git a/requirements-dev.txt b/requirements-dev.txt
new file mode 100644
index 0000000..822131f
--- /dev/null
+++ b/requirements-dev.txt
@@ -0,0 +1,5 @@
+wheel
+pip
+twine
+ipython
+pudb
diff --git a/requirements-test.txt b/requirements-test.txt
new file mode 100644
index 0000000..ca32388
--- /dev/null
+++ b/requirements-test.txt
@@ -0,0 +1,7 @@
+flake8
+mypy
+typing-extensions
+rst2html5
+pytest
+pytest-cov
+codecov
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..adcf504
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,4 @@
+setuptools
+pathlib2
+typing
+click