Upgrade osmium dependency and move away from pbf_parser for historical data

[jenningsanderson]

The new libosmium library maintained by osmcode.org (same author, joto) does all the PBF parsing we need, and does it much more intelligently. As such, PBF import tasks should be ported to use pyosmium, the Python bindings for libosmium so we can take advantage of the speed and caching for geographic points -- these can be fed into bulk imports to PyMongo, creating our preferred Mongo datastructure with much less hassle.