MSBuild snippet is broken

The snippet is not working at all because:
* MSBuild is not usually in the path, .NET 4 on x64 seems a common choice
* /REBUILD is not an option for MsBuild, the correct option is /T:rebuild
* /CFG is not an option for MsBuild, configuration should be set as a build parameter through /P:
* /m allows msbuild to perform parallel builds if possible
Merge pull request #2 from alanta/patch-1

MSBuild snippet is broken