Model template refactor

urbansim's main user interface is that it compiles JSON configuration files into Python files that run various parts of the overall simulation. Here I've refactored all of that a bit:

- Moved the model template files to synthicity/urbansim/templates
- Renamed the template files to *.py.template so that installers don't confuse them as Python files
- Applied PEP8 formatting to the templates
- Added tests that build each of the templates and run them through Python's compiler to make sure they are valid Python
- Added a compilation command line entry point so that a `usimcompile` script is automatically installed for users when they install urbansim (I'm open to suggestions on the name)
- Added tests of the command line interface

This PR has the very first unit tests for urbansim! :fireworks: