Accept Symfony 2.2 in composer requirements

there was a nasty error message using symfony 2.2 and the bundle as composer tried to install the symfony framework bundle from symfony 2.1 and symfony did not like that.

And: I changed the php driver lib  to version 1.2.*, not sure if this is a brilliant idea (I personally like to be on non-dev-branches wherever possible).

And: some additional instructions how to get the bundle from Github using composer