Use profiles to specify cassandra versions

Default is to 1.0.8.  Additional versions can be specified using the following profiles:

    cassandra-1.1
    cassandra-1.2

A nice side effect is that the tests run much faster using Cassandra 1.2. See [this gist](https://gist.github.com/gdusbabek/d20fae204dafbcbeebff) for a comparison.

Spoiler: on my machine 1.1 tests take 139 seconds versus 55 seconds on Cassandra 1.2