`/install` is a skimpy page that points to a more thorough page, `/installing-python-and-numpy-guide`. It feels frustrating to visit the page, get inadequate instructions, and be pointed elsewhere for the real skinny. I suggest we eliminate that page and rename `installing-python-and-numpy-guide` so the `install` nav link points to it. A short intro section can take the place of the current `install` page if we feel an overview is needed.