working on guide for choosing colormaps. Have overview section and start on a few others.
added colormaps guide to beginner guide
Stop make.py removing generated documentation figs
Fix memory leak in FT2Font.
Fix memory leaks in the temporary rasterized images.
Fix memory leaks in the test suite.

This works by avoiding storing a reference to the figure in the
"do_test" enclosure in the image_comparison decorator.  nose keeps a
reference to all of its test functions, and thereby holds on to every
figure in every test that uses the image_comparison decorator (which is
most).  Instead of using the figure in the outer scope, this just uses
the figure number, and then it's looked up when the test function is
actually run.

Also adds gc.collect() so we can ensure there are zero figures in memory
at the start of each test.  Probably not strictly necessary, but it
makes analysing memory usage easier.
Merge pull request #3269 from mdboom/artifacts-master-only

Upload artifacts only on main repository.

Changes to .travis.yaml only.
Merge pull request #3253 from dmcdougall/fix-sphinx-links

Stop make.py removing generated documentation figs
Merge pull request #3258 from mdboom/ft2font-memleak

Fix various memory leaks discovered through valgrind
replaces epd and pythonxy with anaconda and canopy. Also, added some notions in
the readme.osx
adds dyld_fallback_library_path
removing pythonxy
reformatting for line length
redhat->linux
drops pylab reference
getting rid of extra space
both are good distributions
conda libpng and freetype don't help
Two
moves libpng from optional to required