Add instructions for Jekyll on Windows

I added a Windows version of the Jekyll instructions, and made sure that the gemfile would install the necessary gems.
That didn't seem to be working, although I can't confirm that right now. In both these cases I ran in to problems where things wouldn't install correctly. If I just installed the wdm gem and didn't add it in the gemfile, it exploded and didn't work; same thing if I just installed the gem. I guess I can delete these for now, and I can run some more tests from start-to-finish when I get a chance to make sure it works.