Added radial wavefunction for 2D QHO.
Added documentation for radial wavefunction for 2D qho.
Changed qho dependency from scipy to numpy.

We still depend on scipy for the special functions.
Added numpydoc extensions and formatted coulomb docstring.

The numpydoc extensions make for nicer docstrings, both the bare
(terminal) format and the html format.
Added a Makefile to build the tutorials.

Removed the build product qho.rst and added a Makefile to build the
tutorials from ipython notebooks.

Keeping both ipython notebooks and rst files was a little wasteful as
all the images had to be duplicated.
Changed to using pngmath for docs.

This is in line with numpy.
Changed qho docstrings to follow numpy convention.
Updated docs/qho.rst.

Changed introductory text and put in link to tutorial. Added
autosummaries for the methods.
Renamed coulomb eigenfunction -> psi_radial.

Added some examples to the documentation.
Updated docs for coulomb.rst.
Added radial2spherical.

Updated qho to use it when making spherical wavefunctions.
Integrated wfnutils in the documentation.