split Git for Windows and msysGit into two pages

We put the download link for git for windows on the main page and the
link to the development environment to a second page. This way people
should not get them both confused that often anymore.

Signed-off-by: Heiko Voigt <hvoigt@hvoigt.net>
Merge pull request #7 from msysgit/hv/split-msysgit

split Git for Windows and msysGit into two pages