Pywavefront

* Support objects with one vertex statement

* Properly handle face lines with unspecified normal index such as `1/2/`

* visualization: objects without lighting will now have their ambient
color set using `glColor`.

* Textures will now use `GL_REPEAT` by default (as the specificiation suggests)
* Added support for parsing texture options in materials.
The following options are parsed: `blendu`, `blendv`, `bm`, `boost`, `cc`,
`clamp`, `imfchan`, `mm`, `o`, `s`, `t`, `texres`
* Added `options` property to `Texture` class
* visualization now respect the `clamp` option. If `on` the texture will use
`GL_CLAMP_TO_EDGE`. Otherwise `GL_REPEAT` will be used.
* All example windows can now be resized

* Pywavefront is now using `pathlib` internally. `Path` instances can also
be passed to all parsers.
* Bug fix: Texture paths in materials should no longer be mangled when
containing spaces or special characters. It should always be read
exactly as it appears in the file.
* Texture: `file_name` property added as a more robust way to get
the texture file name without path. This should even work for
hard coded windows path on Linux and OS X.
* Texture: Added `find` method searching for the exact texture name in a directory
and all subdirectories. By default it will search from the obj file's location.
* Visualization: `draw` methods now supports `lighting_enabled` and `textures_enabled`
making the user able to toggle on/off lighting and texturing.
* Visualization: Now works with NPOT textures (texture whose dimensions are not powers of 2)

* Fixed an incompatibility issue related to image loading in pyglet 1.4.x
* Texture instances now store the texture name as they appear in the material
and an optional path parameter that represents the absolute path to the
texture.
* Removed dead code related related to python 2/3 compatibility