Releasing Voldemort 1.8.12

Release 1.8.12 on 08/11/2014

* Speeds up vector clock serialization.
* Adds a clean up task in the Gradle build that fixes an intermittent issue with builds on mac.
* Expands test configurations.
* Some fixes and clean ups in the C++ client.
* Rewrites RequestCounter so that it leverages the Tehuti metrics lib.