Add instructions for installing the squadgen conda package

[xylar]

This merge also includes some reformatting of the README.md to be in Markdown format.

[xylar]

This builds off of #7 so I've left it in draft mode for now.

[xylar]

@paullric, let me know if my reformatting of the README.md is something you'd prefer not to do. You can see a preview at:
https://github.com/ClimateGlobalChange/squadgen/blob/51e9ec49602fb4424062e257a2dd057611c8f3a9/README.md
I just wanted to make it a little more readable in Markdown as GitHub renders it but I completely understand if you'd rather keep it in more of a text format like you had it. I can add the conda package instructions in the same style.