Builds status of pull requests

I think branch 2.0.0 must be stable, so builds of pull requests must be successful.

Now builds are successful even if tests failed in it.

@phalcon Could you please check build status of pull requests before merge
@akaNightmare 
your pull request #2974 brokes all tests in 5.3 and adds 2 failures in 5.5+ (https://travis-ci.org/phalcon/cphalcon/builds/40434159)
and #2982 adds one new failure in php 5.5+ (https://travis-ci.org/phalcon/cphalcon/jobs/40434388)