Climlab

With this release, climlab is now fully Python 3 compatible!

Other goodies include:
- improvements to the documentation
- a recipe for building climlab with `conda-build` is now included
- a few bug fixes and minor enhancements

This release fixes some issues with the source distribution that are causing problems building on conda-forge.

No changes to climlab functionality.

This release includes yet more refinements to the build procedure, moving toward a fully automated build on `conda-forge` (hopefully coming in climlab release 0.6!)

Unused parts of the RRTMG_SW and RRTMG_LW source code (the `column_model` versions) have been removed from the `climlab` repository.

This version includes pristine, unmodified copies of RRTMG_SW and RRTMG_LW source code downloaded from [AER](http://rtweb.aer.com/rrtm_frame.html), along with (very slightly) modified forms of a few Fortran code files for climlab.

A few under-the-hood changes to the build procedure hopefully paving the way for automatic builds with conda-forge (stay tuned!)

The source distribution was broken in v0.5.1.

This update fixes the source distribution so the tarball available from pypi actually works.

No changes to user functionality.

Many under-the-hood changes to the wrappers for Fortran radiation components (RRTMG and CAM3) to make it easier to build the package on different systems.

Building with `python setup.py build` or `python setup.py install` now uses `numpy.distutils.core.setup` which automates the building of Fortran extensions with `f2py`.

Installing climlab from pre-built binaries using `conda` is coming in the near-future.

There are no new changes to the public API.