tests/wkb_test:

PEP8 fixes
wkt:

Implemented `load` and `dump`.
wkb:

Implemented `load` and `dump`.
wkb:

Simplified the `dumps` interface and document some limitations of GeoJSON and
the resultant assumptions we need to make. Basically, it's about the ambiguity
of Z and M geometry types: in GeoJSON, 3D geometries do not differentiate
between Z and M, unlike WKT/WKB standards.
tests/wkb_test:

Update test to match the simplified `wkb.dumps` interface.
tests/wkb_test:

Skip `test_dumps_point_m` and explain why (with a comment).