Minor changes:

1. Clean up row template whitespace
2. Remove some debugging and commented code from the render container
directive

[skip ci]
Integrate travis jobs with gitter.im
Always notify gitter.im on successful build:
Added prereqs to tutorial.
chore(Docs): Fixes #1372

Add example of default sort state.
Merge branch 'master' of https://github.com/angular-ui/ng-grid