Tessagon

Many, many changes:

* Nascent test suite
* Linting with Flake8
* CI with Travis
* Start of PyPI packaging (i.e., distribution via pip)
* Updated and more automated documentation and demos

And many more tiling types:

* SquareTri2Tessagon
* DodecaTriTessagon
* DissectedTriangleTessagon
* DissectedHexQuadTessagon
* DissectedHexTriTessagon
* PentaTessagon
* Penta2Tessagon

Includes:

* Eight color patterns (from Grünbaum & Shephard) for SquareTessagon.
* Documentation refactor (2)
* Moving the documentation of all Tessagon classes to own file.
* Make the tile class a class property for each Tessagon class
* Make the color pattern stuff more automatic and allow Tessagon
classes to inspect how many color patterns there are.
* Let tessagon demo figure out how many color patterns to draw.
* Let documentation image script figure out what it needs to render.
* Modify the documentation images script to create thumbnails.
* Adding thumbnails for all classes to documentation
* List how many color patterns each class has in README

Includes:

* A few more Tessagon types;
* Support for color patterns;
* Refactor of demos to reduce churn of the binary blender file and to share more code between the Blender and VTK demos;
* A script to create the images of the Tessagon tilings used in the documentation;
* Enhanced documentation.

This release includes 12 tessellation patterns.