Rearrange Windows setup instructions to be more intuitive

The current order risked students running the SWC installer
before installing either Python or GitBash (one of which is a
dependency depending on the installer).

The instructions also risked it sounding like it would install
everything instead of just adding a few extra pieces.
Merge pull request #1 from ethanwhite/gh-pages

Rearrange Windows setup instructions to be more intuitive