allow constructing a multipoint from a list of points
Merge branch 'master' into documentation-project
as json test with string data
add crs to geojson output
add read support for geojson crs (needs tests)
add a couple more crs
finish geojson read crs impl
work on capitols example
Merge branch 'master' into documentation-project
split vector_io_tests off of vector_tests
add data and properties slots to guppy interface tuples
add custon json encoder to handle numpy types
write CRS to geojson
Merge branch 'master' into geojson

Conflicts:
	karta/vector/geojson.py
add new json test data
add featurecollection test
implement read_geojson_features in vector.read (needs test)
make getcrs method public; remove useless try block; remove properties fields from interface tuples
return one geometry per feature
enforce tuple vertex for comparing points