Support for Symfony 3

[TobiasXy]

It would be nice to have this bundle support Symfony 3.

[GSokol]

+1

[xela007]

+2

[rbtmathieu]

+1

[jalso]

+1

[Max-Yudin]

+1

[ChristianRiesen]

I made a MR in #24 that should at least fix the install-ability of it.

[jrjohnson]

What is it that doesn't work? We're using this bundle currently with 3.3.4.