Update to CMake 2.8.12.2 as 2.8.12.1 has some serious issues.

CMake 2.8.12.2 introduced support for XCode 5.1 which allows support
for Mavericks, also it fixed a bug when a projects minimum required
version was 2.8.12.
Merge pull request #248 from robertmaynard/update_cmake_version

Update to CMake 2.8.12.2 as 2.8.12.1 has some serious issues.