Heaps of changes

Added render code for displaying US areas, preliminary summarizing code for outputting HTML reports, and moved separate `parallel.py` script under `openaddr` module where it can be tested more thoroughly. @iandees you may want to rebase your in-progress branch onto [5df142f](https://github.com/openaddresses/machine/commit/5df142fa236b6b7395f7cf71ebe70d3696fc5028); I can help.