Updated to latest gems and tested with cassandra 0.7

[cirode]

We are using cassandra object in one of our projects having decided that updating this gem was easier and better than creating a model base ourselves. The following changes have been added

1. Vendorised cassandra 0.7 (and added a developer section to the README) to allow developers to run the tests without having cassandra installed locally
2. Updated the gems (and gemspec) to the latest versions
3. Fixed all the current tests to cope with the changes in gems

If you are amenable to it, we will be added support for cassandra/0.8 and other small enhancements as we need them for this project and these will form additional pull requests

[fuentesjr]

+1 Please approve.

[matthuhiggins]

We also have a maintained fork at https://github.com/gotime/cassandra_object. The history that it was forked was lost because it started as a private repo.