Added PHP 5.6 and HHVM to travis.yml

[Nyholm]

I also want to make sure it works with different versions of Symfony2

[mmoreram]

Maybe you should add hhvm to the allow failures block :)

[Nyholm]

Why? The tests passes on HHVM... We want to keep it that way, right?

[mmoreram]

yes, but we have to consider also new features, with new possible dependencies. And we cannot ensure right now than new features will be compatible.

So, imho, we should ensure 100% than new features will be compatible until 5.6

[Nyholm]

Let's worry about new features and possible new dependencies in the future... If we (for some reason) need an dependency that is not supported in HHVM, lets add allow_failures: hhvm at that time then.

[mmoreram]

And how do you want to ensure the BCBreak? I mean, are you defending that some project are using right now this bundle with HHVM, and someday maybe is not ready for that? Is it right for you?

[Nyholm]

This PR removes PHP 5.5 from allow_failures. Are you saying that this bundle might add "new features, with new possible dependencies" that is supported by PHP5.4 but not PHP5.5? Sure, HHVM is not 100% compatible with PHP at the time of writing. But each week the compatibility will increase... not decrease.

BCBreak? What are you talking about? If you develop a new feature that can't run on all the supported platforms, that's not a Backwards Compatibility break. If you really need that feature, make sure to write it in a way that works with HHVM. If it is impossible, just disable the feature for HHVM only.