msysgit.github.com Site Redesign

As discussed in https://github.com/msysgit/msysgit/pull/99 I have redesigned the Git for Windows project site and am submitting my idea for the new site here.  I expect that the textual content of the site will need revision as I have made some assumptions when writing it.  As for the site design, I welcome any requested modifications and / or commits by others.  

Feel free to edit!