Updated install.rst to make it easier to find official binary downloads.
uddated install to make it easier to find stand-alone package info.

As per discussion on a previous pull request, and the numpy list, a new version -- it emphasizes that this is about the "stack", and provides additional info about how to get individual packages.

I pulled out the Homebrew instructions -- I haven't tested them myself, we shouldn't out that in without some good testing.
Change title of the 'Custom' section, remove Homebrew instructions, fix typos
Merge branch 'pr-32'