add travis and coveralls integration

make tests compatible with php 5.3

remove hhvm from travis

add coveralls integration

use old array syntax for php 5.3 support

add php 5.3 to the allowed failures for now

add build and coverage indicators to readme
This is due to lack of support for PHP 5.3 for certain functions with vfsstream: https://github.com/mikey179/vfsStream/issues/56.