Update Style

* Bootstrap v3.1
* New sidebar
* Minor fixes
Merge branch '2.0-wip' of github.com:YOURLS/YOURLS into 2.0-wip

# By Léo Colombaro
# Via Léo Colombaro
* '2.0-wip' of github.com:YOURLS/YOURLS:
  Delete CHANGELOG.md and prefer /releases pages