Made instructions clearer

[dbenamy]

This tries to make the docs clearer in a few ways:

1. Adds explicit instructions for setting up [paths] and assumes that most people will want to do this.
2. Adds headings to more clearly differentiate between cloning and pushing an existing repo.
3. Trims some text that should be obvious to anyone using this. Basic hg usage is probably out of scope.
4. Shuffles things around a bit and dedupes for better general organization.

Before

After