1. fixed typos, latex errors, and improved readability of text

2. Restructured function docstrings to comply with numpy's guidestyle
3. Added ODE derivation of Newtonian equations of motion
4. Added legend to origins scatterplot
5. Fixed issue with passing in future covariates into exogenous model when forecasting
6. Added model evaluations and comparisons
7. Fixed issue with diffuse initialization of P0

Author: Dekermanjian