Merge pull request #13 from abinashpanda/dev

Dev
Added mailing list
add coveralls
Merge branch 'dev' of https://github.com/pgmpy/pgmpy into dev
Add coveralls badge
updated cover-package
add .coveragerc
updated exclude_lines in .coveragerc
Rename ExceptionsPgmPy.py to Exceptions.py
shifted _string_to_tuple to the top
added example to docstring for add_nodes
added example to docstring for add_edges
Removed the alphabetical sorting when adding to _parents of a node
Added MissingStatesError and ExtraStatesError
Added validations for checking missing/extra parents and states in set_rule_for_states and set_rule_for_parents
Added basic definition for TabularCPD
Fixed np.Array to np.array
Fixed PEP8 non-compliance
Changed set_tabularcpd to add_tabularcpd and get_cpd to return the CPDs.TabularCPD.table
Split _all_states_mentioned into two functions: _no_missing_states and _no_extra_states
Split _all_parents_mentioned into two functions: _no_missing_parents and _no_extra_parents
Changed name of set_observed to add_observation
Changed the default behaviour to expect only one observed state in a node. Modified #TODO accordingly.
Changed the name of reset_observed to reset_observed_nodes. Changed the default argument in it from False to None.
Changed the Example in docstring of active_node_trails to reflect the new function-names
Changed the docstring of the class BayesianModel to reflect the changes in the function-names