release version 0.7
Changes:
- major refactor of geometry hierarchy
- adds Multiline and Multipolygon classes
- polygon vertices are double-nested in order to represent sub-polygons
- only multipart geometries now contain a data attribute
- GeoJSON now attempts to project all data to geographical WGS84 coordinates as
per https://datatracker.ietf.org/doc/draft-ietf-geojson/
- `force_wgs84=False` can be set to avoid this behaviour
- multivertex geometries now use CoordString as a data backend, which should
permit faster operations on the C side
- rename `Line.subsection` -> `Line.to_npoints`
- new R-tree implementation in C
- `projected` keyword argument added to `Point.distance`, `Point.azimuth`, and
`Point.walk` to control whether geodetic or planar algorithms are used with
the CRS is not geographical
- replaced polygon membership testing algorithm with a winding number-based test
- implemented fallback algorithm for polygon membership testing in polar regions
