* Add flake8 config file

* Fix flake8 for test files

* Add tests to CSP class

Add test for the following methods on CSP class:

* assign
* unassigns
* nconflits
* actions

* Refactor some asserts in test_csp.py

Some asserts were being done in the following way:
assert (X is not None) == True

Now, they are handled in the following way:
assert X

- Added tests for PluralityLearner, NaiveBayes and kNN algorithms

- Replace parse_csv with non-trivial input

* Added implementation of the cake problem

* Added test for three_block_tower and fixed a bug in three_block_tower code

Added test for spare_tire problem of planning module.

* Implementing HITS algorithm

* Moving HITS work to nlp.py and test_nlp.py

* Added Action class for PDDL

* Added tests for Action class

* Changed doc string

* Added PDLL class

* Added Air-Cargo-problem

* Tested Air Cargo Problem

* Replaced mean with standard lib function introduced in 3.4

* #TODO Replaced every with all

* Proper names for variables introduced in 2to3 conversion.

* modifies Fig. to Figure all over the repository

* fixed a small type in logic.py

Following a suggestion by C.G.Vedant, changed |implies| to |’==>’|

* removes obsolete Fig dictionary from utils.py

* modified rl notebook according to the new Figure conventions

* removes 'import Fig' and changed the names of Figures

* fixes a small error (by me) in executing the cells in rl notebook

*  Used isclose from utils to maintain compatibilty for 3.4

* Removed redundant distancesquared function

* Removed duplicate definition of clip in grid.py and used import from instead.

* Fixed spelling typo

* Made Log Usage Consistent in text.py

* Added Explicit Imports from utils

* temporary fix for eliminate_implications

* Change from << to <==

* Fixed implies operator in SAT_plan

* changed Expr name to counter

* Fixed a typo in logic.py

* Added translate_to_SAT()

* extract solution from model

* added test cases

* removed debug code

Add InfixOps, refactor expo and Expr

* changes a typo of file name to /aima-data

* modified some documentaion and removed doc tests

* changed the names like Fig[2, 3] and added unit tests for search.py

* adds Fig[4.23] graph which is 1-dim state space problem

* adds LRTA star agent class

* adds fully implemented LRTA star agent

* adds tests for LRTA star agent