Added some function arguments to the documentation for FuncAnimation
Fix mpl_toolkits hyperlinks
Fix hyperlinks to pylab_examples
Fix auto-closing in PolyCollection
Add test png
Merge pull request #3239 from mdboom/polycollection-closed

Fix auto-closing in PolyCollection
Remove dregs of nxutils
Fixed backend workflow.
Merge pull request #3004 from mdboom/docs-nxutils

FAQ and unit/ still refers to nxutils
Merge pull request #3246 from dmcdougall/fix-doc-links

Fix some hyperlinks in the documentation

Edits only in rst files
Merge pull request #3243 from pelson/nbagg_proper

Fixed backend workflow.
Merge pull request #3217 from JulianCienfuegos/master

Added some function arguments to the documentation for FuncAnimation
Upload artifacts only on main repository.
Merge pull request #3269 from mdboom/artifacts-master-only

Upload artifacts only on main repository.

Changes to .travis.yaml only.
Add documentation to Travis builds.
Minimize matrix.
Fix syntax.
Install Sphinx for docs build
Fix logic
Fix logic.