Merges in CASinoCore logic

I went ahead and merged in all CASinoCore functonality into CASino as discussed in rbCAS/CASinoCore#18 and based on the work I did in rbCAS/CASinoCore#12

A couple things to note:

* The authenticator gems will need to be forked to remove the `CASinoCore` namespace
* I removed the namespaces for `CASinoCore::Builder`, `CASinoCore::Processor`, and `CASinoCore::Authenticators` due to how Rails' autoloader works. These are now `CASino::TicketValidationResponseBuilder` and `CASino::LogoutProcessor`, etc.

  The change from `CASinoCore::Authenticators::MyFancy` to `CASino::MyFancyAuthenticator` will obviously affect the ActiveRecord and LDAP authenticators. I decided to go ahead and force the issue because those gems will have to be forked and re-released anyway to remove the `CASinoCore` portion. Removing the `Authenticator` namespace brings CASino in line with how projects like Devise define their community plug-ins (i.e. [here](https://github.com/nbudin/devise_cas_authenticatable) and [here](https://github.com/cschiewek/devise_ldap_authenticatable))
* Fixed the `Casino` Rails generator [namespace inflection issue](https://github.com/dlindahl/CASino/commit/7afa68677edfbcb20a71a1bf6e5c597d2f594665)

I had originally wanted to [retain the history](https://github.com/rbCAS/CASinoCore/issues/18#issuecomment-22454012) of CASinoCore during this work, but I couldn't get it to work properly and ultimately punted on it. If everyone feels very strongly about keeping the history (which is reasonable), then at the very least this will show everyone the level of work required to do this merge.

Once again, this is in a "Works for me" state and all the tests pass. It would probably be worth some more extensive testing by the team.