Added ".exe" extension to binary file on Windows

Running a binary on Windows does not work if it does not have the ".exe"
extension. No joke!
Kill process before rebuild

If the process is not killed before the rebuild starts, it will fail on
Windows as the "bin" file is still running, thus open & locked.
Merge pull request #7 from JamesClonk/windows_exe_extension

Added ".exe" extension to binary file on Windows