Version Selector (#4386)

* Show current version of docs in nav

* Branch in edit link

* WIP version selector

* An actual working but not pretty version dropdown

* update URLs for versions

v1.7: https://kubernetes.io/docs/home/
v1.6: https://v1-6.docs.kubernetes.io/docs/home/
v1.5: https://v1-5.docs.kubernetes.io/docs/home/
v1.4: https://v1-4.docs.kubernetes.io/docs/home/

* fix v1.4 and v1.5 paths

* Tidier drop downs

* Make font visible always

* Make background match main nav always

* change to major.minor version number

* show only major.minor version in drop down list

* switch from githubbranch to docsbranch

* update githubbranch

* update githubbranch values

* Border radius for bottom of dropdown

* Tabs are hard

_config.yml

@@ -22,6 +22,27 @@ defaults:
       version: "v1.7"
       githubbranch: "master"
       docsbranch: "master"
+      versions:
+        - fullversion: "v1.7.3"
+          version: "v1.7"
+          githubbranch: "v1.7.3"
+          docsbranch: "release-1.7"
+          url: https://kubernetes.io/docs/home/
+        - fullversion: "v1.6.8"
+          version: "v1.6"
+          githubbranch: "v1.6.8"
+          docsbranch: "release-1.6"
+          url: https://v1-6.docs.kubernetes.io/docs/home/
+        - fullversion: "v1.5.7"
+          version: "v1.5"
+          githubbranch: "v1.5.7"
+          docsbranch: "release-1.5"
+          url: https://v1-5.docs.kubernetes.io/docs/
+        - fullversion: "v1.4.12"
+          version: "v1.4"
+          githubbranch: "v1.4.12"
+          docsbranch: "release-1.4"
+          url: https://v1-4.docs.kubernetes.io/docs/
   -
     scope:
       path: "docs"