Information Gathering Agent and probability notebook update (#931)

* Formatting fixes

* Added runtime comparisons of algorithms

* Added tests

* Updated README.md

* Added HMM explanation and contents tab

* Added section on fixed lag smoothing

* Added notebook sections on particle filtering and monte carlo localization

* Updated README.md

* Minor formatting fix

* Added decision networks and information gathering agent

* Added notebook sections for decision networks and information gathering agent

* Updated README.md