Mapbox-vector-tile

- Include LICENSE & CHANGELOG.md in sdist tarballs
- Refactor geometry encoding logic, including skipping tiny geometries
- Decoded geometry is now geojson-ish dict
- Winding order is now optional
- Add benchmarking around round function and document how to improve performance
- Document performance tip for protobuf encoding with C bindings for Debian

- Generate more valid polygons and multipolygons using [pyclipper](https://pypi.python.org/pypi/pyclipper) library for v2 MVT compliance (but we're still not fully v2 compliant for [other](https://github.com/tilezen/mapbox-vector-tile/issues/42) reasons).
- Handle edge cases where polygon buffer makes a multi-polygon, ensuring inner rings are dropped when subtracting them from the polygon would make it invalid, and not adding multipolygons as array elements for multipolygon constructor.
- Calculate area more properly by using PolyTree result from Clipper.
- Factor out polygon validity code into its own file.

- Improved results from `on_invalid_geometry_make_valid` when the geometry is self-crossing. It was possible for large parts of the geometry to be discarded, and it is now less likely. See [PR 66](https://github.com/tilezen/mapbox-vector-tile/pull/66) for more information.

- Custom rounding functions: a `round_fn` parameter was added to the `encode` function, which allows control over how floating point coordinates are transformed to integer ones. See [PR 55](https://github.com/tilezen/mapbox-vector-tile/pull/55).
- Custom validity functions: an `on_invalid_geometry` parameter was added to the `encode` function, which is called when invalid geometry is found, or created through coordinate rounding. See [PR 46](https://github.com/tilezen/mapbox-vector-tile/pull/46).
- Winding order bug fix: See [issue 57](https://github.com/tilezen/mapbox-vector-tile/issues/57) and [PR 59](https://github.com/tilezen/mapbox-vector-tile/pull/59).
- Performance improvements: including a 2x speedup from using `tuple`s instead of `dict`s for coordinates, see [PR 56](https://github.com/tilezen/mapbox-vector-tile/pull/56).
- Improvements to PY3 compatibility: See [PR 52](https://github.com/tilezen/mapbox-vector-tile/pull/52).

- python3 compatability improvements
- travis integration
- documentation updates
- insert CMD_SEG_END for MultiPolygons
- decode multipolygons correctly
- encode tiles using version 1

- include README.md in distribution to fix install