Adding travis & coveralls

MINT-1580
Updating composer

MINT-1580
Adding PHP 5.6

Setting allowed failures for 5.6 & hhvm
Merge pull request #3 in MINT/php-checkout from MINT-1580_adding_build_status_images to v1.2

* commit '17a5a8ed35e7361cdf75906badfcd298cd9bf41d':
  Adding PHP 5.6
  Updating composer
  Adding travis & coveralls