Update Travis to start running tests on PHP 5.5

Allow travis to test PHP 5.5 alphas and allow failures for now.
Revert "Merge branch 'hotfix/3424'"

Reverts #3424 due to BC issue reported in #3576

This reverts commit c8c637523fe1a5705ba01684386a8ef63e675464, reversing
changes made to 054f7a0f95bb919cce95faa53ced0a525017602f.
Merge branch 'patch-1' of git://github.com/mwillbanks/zf2 into feature/3601
Merge branch 'feature/3601'

Close #3601
Merge branch 'master' of https://github.com/zendframework/zf2