Fix memory leaking. HostConnectionPool intances are being retained forever
Make HostConnectionPool IDisposable

- Unsubscribe to Host.Down event when disposing
- Invoke Connection.Dispose() from the pool
Test that having a disposed Session created by the cluster does not affects other Session instances
Version bump
major refactor to improve/stabalize integration tests
Merge pull request #54 from askmyc/2.1

major refactor to improve/stabilize integration tests
ConnectionTests and RequestHandlerTests set test category
Dispose SocketAsyncEventArgs when closing the connection
Merge branch '2.1' into mapping

Conflicts:
	src/Cassandra.IntegrationTests/Linq/LinqSessionTests.cs