gc_enable is not called if running with HHVM

Since HHVM doesn't support garbage collector (for obvious reasons), the following patch make Ratchet works with HHVM as well.
Remove composer.lock to correctly test the library with last version
Add composer.lock to gitignore
Update dependencies to use last stable version of guzzle
Skip test when pdo_sqlite isn't there but PDO is
Updated docs
Attempting HHVM on Travis, using installed composer
[Tests] Added AB LibEv to suite, cleaned up scripts
[App] Use trigger_error instead of echo
Support for React 0.4
Enforce UTF-8 in App (disallow mbstring.func_overload)
Added subscribers filtering in topic broadcasting for taking into account exclude & eligible data
Slightly modified TopicTest to support new broadcast params
Code fix for pull request 165
[WAMP] CS, added unit tests for new features, 100% on WAMP
[Session] Attempting to fix broken HHVM unit test
[Sessions] Trigger error when circumventing HHVM bug
Test added