Ogm 194 (Support Redis as Datastore)

Hi,

I've added support for Redis as a DatastoreProvider. All tests pass but there are two things that I would like you to keep in mind as below.

1. Reids needs to be run before typing the command, `mvn clean install`. Please download and run Redis before the command from [here](http://redis.io/download).
2. `RedisDialect.getLockingStrategy` method currently throws an exception. Implementing this method correctly needs help from Redis community. Once getting how to map lock strategies on Redis, this method will be implemented.

I've been trying to make each commit as small and meaningful as possible. However, if you have some issues with them, please let me know. I'll fix them.

Thank you
Seiya