Super counter column support + unit tests + unit test bug fixes

Changes in this pull request:

* Added an overload to `InsertCounterColumn` which accepts a SuperCounterColumn as an argument
* Added a new test fixture to **FluentCassandra.Integration.Tests** which tests `InsertCounterColumn` for regular counter column families as well as super counter column families.
* Fixed a bug with `InsertColumn` tests - the SuperCounterColumn test wasn't actually reading its results from the super counter column family, and only passed because the data stored in the regular column family it was reading from just happened to share the same expected values.
* Modified the test fixture setup such that it adds a new `SuperCounter` family to the Testing keyspace.