* tic-tac-toe gui added

* Added GUI for Searching

* Added Legend and Minor Fix

* Minor Fix and Options added

* Added Breadth-First Tree Search

* Added Depth-First Tree Search

* Minor Fix

* Added Depth-First Graph Search

* Minor Fix

* Breadth-First Search and Minor Fix

* Added Depth-First Graph Search in notebook

* Added Depth-First Tree Search in notebook

* Cell Placement

Closes #673

* tic-tac-toe gui added

* Added GUI for Searching

* Added Legend and Minor Fix

* Minor Fix and Options added

* Added Breadth-First Tree Search

* Added Depth-First Tree Search

* Minor Fix

* Added Depth-First Graph Search

* fixed Key Error bug in CustomMDP and reordered the return values of T function to be consistent with GridMDP

* removing idea files from git

* probability notebook

* Update test_probability.py

* Update README.md

* add failure_test method to utils

* comment fix

* Update test_learning.py

* Update test_csp.py

Throw away the second argument returned by enumerate as we do not use it. Otherwise, name `_` arg simplify the rest of this function using the returned values rather than just indexes.

* Updating Submodule

* Create SUBMODULE.md

* Update notebook.py

* Update notebook.py

* Update nlp_apps.ipynb

* Update test_text.py

* remove mnist from learning.ipynb

* add learning applications

* Update notebook.py

- remove duplicate psource
- add section headers
- add mdp visualization code

* Update nlp_apps.ipynb

* Update csp.ipynb

* Update mdp.ipynb

* Update games.ipynb

* Update README.md

* Update intro.ipynb

* Added predicate_symbols

* Added FOIL

* Updated README

* Update README.md

* Create nlp_apps.ipynb

* typo in readme

* Update intro.ipynb

* Added tests for search.py

* Updated readme

* Removed extra newline

* Fixed seed

* Update README.md

* Added docstring for minimal-consistent-det

* Update knowledge.ipynb

* Update notebook.py

* Update knowledge.ipynb

* bringing it all together in notebook

* add a simple naive bayes classifier

* Update test_learning.py

* spacing

* minor fix

* lists to strings

* Added python code for psource (#613)

* added psource code with optional highlighting (#613)

* Update notebook.py

* Update nlp.ipynb

* line ran too long; shortening

* Update nlp.py

* add chart parsing test

* add chart parsing section

* add cnf_rules to grammar

* Update nlp.ipynb

* Update test_nlp.py

* add more to CNF section