add release branch tags and merges

@jcounts @ksnavely 

Finally got the release command up and running. 
Works in cirrus_test example:

git cirrus release new --micro
  - Makes a new release branch, bumps the micro version, builds release notes, commits and pushes them 
git cirrus release build
 - Creates the build artifact for upload 
git cirrus release upload
 - merges the release branch into master, develop
 - creates and pushes tag 
 - uploads to pypi server via fabric ssh  


You don't use this function anywhere?