feat(cli): version flag (#60)

* feat(cli): version flag

Adds a --version flag to jb. Only available on go versions greater than 1.12

* style: add license headers

* chore(ci): generate only on latest go

* fix: unique step names

* doc: include version in README help text

* fix: rebuild .drone.yml using drone.cli

* fix: remove race condidion from CI

.drone.yml

@@ -1,6 +1,6 @@
 ---
 kind: pipeline
-name: go1.13
+name: default
 
 platform:
   os: linux
@@ -9,7 +9,7 @@ platform:
 steps:
 - name: gomod
   pull: always
-  image: golang:1.13
+  image: golang:latest
   commands:
   - go mod vendor
   - git diff --exit-code
@@ -21,113 +21,7 @@ steps:
       exclude:
       - tag
 
-- name: build
-  pull: always
-  image: golang:1.13
-  commands:
-  - make build
-  - make test
-  - make test-integration
-  environment:
-    CGO_ENABLED: 0
-    GO111MODULE: on
-  when:
-    event:
-      exclude:
-      - tag
-
-- name: generate
-  pull: always
-  image: golang:1.13
-  commands:
-  - make check-license
-  - make generate
-  - git diff --exit-code
-  environment:
-    CGO_ENABLED: 0
-    GO111MODULE: on
-  when:
-    event:
-      exclude:
-      - tag
-
----
-kind: pipeline
-name: go1.12
-
-platform:
-  os: linux
-  arch: amd64
-
-steps:
-- name: gomod
-  pull: always
-  image: golang:1.12
-  commands:
-  - go mod vendor
-  - git diff --exit-code
-  environment:
-    CGO_ENABLED: 0
-    GO111MODULE: on
-  when:
-    event:
-      exclude:
-      - tag
-
-- name: build
-  pull: always
-  image: golang:1.12
-  commands:
-  - make build
-  - make test
-  - make test-integration
-  environment:
-    CGO_ENABLED: 0
-    GO111MODULE: on
-  when:
-    event:
-      exclude:
-      - tag
-
-- name: generate
-  pull: always
-  image: golang:1.12
-  commands:
-  - make check-license
-  - make generate
-  - git diff --exit-code
-  environment:
-    CGO_ENABLED: 0
-    GO111MODULE: on
-  when:
-    event:
-      exclude:
-      - tag
-
----
-kind: pipeline
-name: go1.11
-
-platform:
-  os: linux
-  arch: amd64
-
-steps:
-- name: gomod
-  pull: always
-  image: golang:1.11
-  commands:
-  - go mod vendor
-  - git diff --exit-code
-  environment:
-    CGO_ENABLED: 0
-    GO111MODULE: on
-  when:
-    event:
-      exclude:
-      - tag
-
-- name: build
+- name: build-1.11
   pull: always
   image: golang:1.11
   commands:
@@ -141,10 +35,47 @@ steps:
     event:
       exclude:
       - tag
+  depends_on:
+  - gomod
+
+- name: build-1.12
+  pull: always
+  image: golang:1.12
+  commands:
+  - make build
+  - make test
+  - make test-integration
+  environment:
+    CGO_ENABLED: 0
+    GO111MODULE: on
+  when:
+    event:
+      exclude:
+      - tag
+  depends_on:
+  - gomod
+
+- name: build-1.13
+  pull: always
+  image: golang:1.13
+  commands:
+  - make build
+  - make test
+  - make test-integration
+  environment:
+    CGO_ENABLED: 0
+    GO111MODULE: on
+  when:
+    event:
+      exclude:
+      - tag
+  depends_on:
+  - build-1.11
+  - build-1.12
 
 - name: generate
   pull: always
-  image: golang:1.11
+  image: golang:latest
   commands:
   - make check-license
   - make generate
@@ -156,5 +87,7 @@ steps:
     event:
       exclude:
       - tag
+  depends_on:
+  - build-1.13
 
 ...