Cluster params & Context name

Hey, 

I just add this because I wanted to connect to a `PasswordAuthenticator` cluster and I wasn't able to do it so I added the alternative of an instantiated `ClusterParams`.

The rest don't change, except from the context name which was confusing with other `Session` you might have in Negroni. You can change that part if you don't like it.
Good call for the library by the way.

Cheers,