Add a ReviewBot for testing patches on Windows

A major hindrance to development of Mesos for Windows is that, since the platform support is so new, no tests their patches on Windows. Frequently this causes upstream commits to master to break the Windows build (a recent notable occasion was commit 5f159cdcb), which interrupts Windows developers (read: me) in order to fix the build. Much of the problem is due to broken processes failing to catch human error.

One process we can immediately fix is the ReviewBot, which tests uploaded patches for Ubuntu. Adding the same functionality but for Windows will go a long way toward preventing upstream build breaks.