Renamed requirements file.
[ref-229] Inplace argument added in the Factor methods.
[ref-230] Moved JunctionTree class from base to models module.
Merge branch 'issue224' of https://github.com/ankurankan/pgmpy into dev
Renamed Inference module to inference module.
[refs-230] Refactored pgmgpy codebase:
    - to create base class for DirectedGraph and UndirectedGraph
    - to change base class for BayesianModel and MarkovModel
Renaming Inference module to inference module in doctests.
[refs-230] Removed unnecessary imports from __init__.py.
Added class for FactorGraph.
Created new JunctionTree class in pgmpy.models module.
Added imports of JunctionTree and FactorGraph in __init__.py of models module.
Renaming of Inference module into inference module in tests_inference.py
Removed commented-out tests from test_factor.py
Merge branch 'dev' of https://github.com/abinashpanda/pgmpy into dev
Modified BayesianModel.py to-
    * fix bug in get_indpendencies
    * fix bug in conversion to markov model
Created methods for finding local independencies and markov blanket.
Docstring changes in Independencies class.
Added method for finding variable nodes and factor nodes in FactorGraph class.
Added method for computing partition function in UndirectedGraph class.
Created docstring in get_independencies() method for BayesianModel.