Update Travis CI config
Update Travis CI config

 - Add hhvm build
 - Change Symfony 2.7.*@dev build to run on PHP 5.6
 - Update composer before running install commsn
 - Prefer dependancy distributions
 - Push code coverage to Coveralls
 - Push code coverage to Scrutinizer
 - Enable Travis' fast finish mode
 - Only build the develop and master branches.

dankempster/axstrad-browser-sync-bundle,dankempster/axstrad-browser-sync-bundle