Adds n_jobs and state_names arguments to DBN.fit method

[ankurankan]

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[codecov]

Codecov Report

Merging #1620 (957232a) into dev (93cebd7) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 957232a differs from pull request most recent head 9faf59c. Consider uploading reports for the commit 9faf59c to get more accurate results

@@           Coverage Diff           @@
##              dev    #1620   +/-   ##
=======================================
  Coverage   93.89%   93.89%           
=======================================
  Files         145      145           
  Lines       17093    17093           
=======================================
  Hits        16050    16050           
  Misses       1043     1043           

Impacted Files	Coverage Δ
pgmpy/models/DynamicBayesianNetwork.py	94.50% <100.00%> (ø)

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