Create a 2.0 branch?

[jeroendk]

Would you consider creating a 2.0 branch where we can commit (possible) breaking changes?

For example:

• Change all the public services to private.
• Add type hint and return types to all methods (where possible).
• Maybe drop Symfony <3 support because EOL, but only if needed.

[Nightbr]

I prefer we merge the last PR for SF2 and release a last version. And after that we publish a 2.0 & drop php5.6 & SF <3. I really don't want to maintain 1.x & 2.x version of this lib.

[Nightbr]

Add to that, I would like to drop the support of PHP 5.6 --> in the v2.0 of this bundle