[ENH] explore and test numba.jit() options

[jGaboardi]

Potential functions:

• network._yield_napts
• network._evaluate_napts
• network._newpoint_coords
• network. enum_links_vertex
• network.allneighbordistances
• network.nearestneighbordistances
• network.split_arcs
• util.snap_points_to_links
• util.get_neighbor_distances