Fixes #7611: fix optgroup formatting for Firefox
Fixes #7474: Use `@input-height-base` in `.navbar-vertical-align()` for `.navbar-form`
Refactor readme to include directions on running jekyll locally
Update contributing file

* Remove notes on repo section
* Update hirearchy of coding standards sections
Back to getbootstrap.dev for jekyll
Merge remote-tracking branch 'upstream/3.0.0-wip'
updates