* fixed typos

* fixed several typos

* Corrected test_compare_agents() function

TrivialVacuumEnvironment was missing a pair of parenthesis while creating the "environment" object of the TrivialVacuumEnvironment class
ModelBasedVacuumAgent and ReflexVacuumAgent were also missing parenthesis while creating the "agents" object.

* Reverted changes made to test_compare_agents()

* fixed typo

* Modified table for TableDrivenVacuumAgent

* Add learing agent

* Add image for learning agent

* Added vacuum_world.ipynb

* Add psource for environment