Added models module for generating coordinates from a file, from random beacon readings, and from random robot movement. Added a simple logging class with no dependencies on other modules that works with Python 2.7.

I'm thinking we need to revise the code slightly to base calculations on beacon readings rather than robot coordinates. For now, filter.py is using the RobotModel, but I think it needs to be changed to use BeaconModel or (to compare against sample data) FileModel.