Renaming the repository to follow best practices

[stof]

The best practices recommend to use the bundle logical name as github repository name to avoid collision for people forking them (forking both FOSUserBundle and SonataUserBundle before the renaming would have lead to have only one repo on your account, but a messed one for instance).
So the repository should be renamed to SensioCasBundle (without changing anything in it except the url in the doc). This has been done just now by FOS and Liip, and will be done for FOQ repos soon, and probably other ones as we are asking people to follow the best practice. The sooner it is done the better to avoid changing the repo url after the stable release.

Note that this is already done for other Sensio repo, which were the first one to apply the best practice (creating it)