http://docs.travis-ci.com/user/build-configuration/#Rows-That-are-Allowed-To-Fail

Fixes #2341, fixes #2317: moved codeception dependecies to "suggest" section, fixed codeception version on stable branch

fixes #1744

avoid failure when it is not started at that point

http://www.hhvm.com/blog/2393/hhvm-2-3-0-and-travis-ci

(coveralls.io still excluded)

The db fixture in the sphinx configuration for unit test takes place
after starting the sphinxserver on travis, by importing the fixture
in the before scripts we allow sphinxsearch on travis to run create
the indexes properly

far better than depending on fat guzzle