Added HHVM and PHP 5.6 to travis-ci

run build against PHP 5.6 and hhvm but allow them to fail to just see how it works.

http://docs.travis-ci.com/user/build-configuration/#Rows-That-are-Allowed-To-Fail
just update the url to 1.1..7RC2 instead of 1.1.0RC3 (and the folder name after decompressing the archive)