added test for count() and mode()

* Update test_learning.py

* Update learning.py

* set max_score to -1 (for now)

* Update learning.py

* Make find_max more pythonic

* Update learning.py

* Add Euclidean Distance

* Update learning.ipynb

* minor fix in notebook

* minor spacing in learning.py

* Added Euclidean Test

* Adds hashable dict type

* Implemented permutation decoder

* added test for permutation decode

* Optimized permutationdecoder

* relaxed tests

* Implement Topological Sort

- Implemented topological_sort
- Added auxiliary function build_topological
- Updated call to topological_sort

* Use defaultdict to build visited

* Added test

* Update csp.py

Skip first item of iteration

* Bugfixing

* Test for "exclude"

* Update test_learning.py

* update_values

* Fix NgramTextModel bug

* Add new tests for NgramTextModel

* Update test_agents.py

pep8 changes, showed flake8 errors

* Update test_agents.py

* Update test_agents.py

* Update test_agents.py

* Update test_text.py

added missing whitespace after comma

* Update utils.py

added space after comma

* Update search.py

added space after comma

* Update probability.py

added space after comma

* Update learning.py

added space after comma

* Update planning.py

added double_tennis_problem

* Update rl.py

In the pseudocode figure 21.8, the first 'if' starts with argument 's', which is the previous state, not s1(i.e, the current state).

* Update search.py

the 'uniform_cost_search' in notebook 'search-4e.ipynb' resembles more to the pseudocode in book.

* Update search.py

* Update search.py

* Update search.py

Add DecisionTreeLearner, NeuralNetLearner and PerceptronLearner tests

* move play_game into games class

* display current state before prompting for action

* fixed player swap bug

* display available moves to human players

* make tests pass

* Added testcase for agents.py

* spacing around commas was wrong

Add test for the following functions from csp.py

* revise
* AC3
* first_unassigned_variable
* num_legal_values
* mrv

* Rearranged Tests

- test_ngram_models to the top
- added test_viterbi-segmentation
- removed test_unigram_text_model

* "test_ngram_models" to "test_text_models"

* added tests for Direction

* fixed Direction arithmetic error

* Update agents.py

* Update test_grid.py

* Update grid.py

Add tests to the following methods from CSP class

* result
* goal_test
* support_prunning
* suppose
* prune
* choices
* infer_assignement
* restore
* conflicted_vars

* 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