* added some test cases to first function in utils.py

* added space after each comma

* Fix typos for Wupus agent

* fix imports

`usa` in csp.py incorrectly has NM not being a neighbor with AZ.

Otherwise `csp.curr_domains` may not be available for the loop that follows.

Shortened it, finding conflicts separately and storing them in different variables has no use later in the notebook; so i believe this looks better.

Corrected typos + minor other text changes

Typos and minor other text errors removed

Made a colored table to display dog movement instead. Corrected grammatical errors, improved the sentence structure and corrected any typos found.

* Revamped the notebook

* A few changes reversed

Changed a few things from my original PR after a review from ad71.

A thank you to contributors from the GSoC 2018 program!

`self.heap.append` simply appends to the end of the `self.heap` 
Since `self.heap` is just a python list. 
`self.append` calls the append method of the class instance, effectively putting the item in its proper place.

Added a few new sentences, modified the sentence structure at a few places, and corrected some grammatical errors.

* added relu activation

* added default parameters

To make it more descriptive and accurate.

To make it more accurate.

Remove unnecessary initial goal test in best_first_graph_search. The loop will catch that case immediately.

* Added KB_AgentProgram and subst

* Added doctests

* Updated README.md

* Fixed doctest

* Fixed doctest

* Fixed doctest

* Added definite_clauses_KB to logic.py

* Fixed a doctest, again

* Fixed another doctest

* Fixed another doctest

* Moved unnecessary doctests to unit tests

* Added unit test for ModelBasedReflexAgent

* Added unit test for ModelBasedReflexAgent

* Updated README.md

* Minor fix

* Fixed a doctest

* Minor modifications in planning_angelic_search.ipynb and knowledge_FOIL.ipynb notebooks.

* Modified FOIL_container

* Added unit tests for FOIL_container functions

* Added knowledge_current_best notebook

* Added knowledge_FOIL notebook

* Added knowledge_version_space notebook

* Added images for knowledge_FOIL notebook

* knowledge.ipynb replaced by knowledge_current_best.ipynb, knowledge_version_space.ipynb, knowledge_FOIL.ipynb

* modify knowledge.py