fix problems running on Windows

Using $HOME environment variable to get user home directory doesn't work on Windows. 
The better way of doing this is 
scala> System.getProperty("user.home")

and calling "gvim" directly from Java doesn't work on Windows:
scala> Runtime.getRuntime().exec("gvim")
java.io.IOException: Cannot run program "gvim": CreateProcess error=2, The system cannot find the file specified

instead should use "gvim.bat"