Master branch is in a broken state

[stof]

The master branch is meant to start the development of 2.0.

Currently, the only thing it tries to do is dropping support for unmaintained versions. But that is broken:

• unmaintained PHP and Symfony versions have already been dropped in 1.3
• the merge of 1.3 into master was broken, and so master is actually dropping support for Symfny 4, which is clearly a maintained version.

I suggest to drop this 2.x-dev branch entirely for now, and start from scratch again once we actually have something to put in the v2.