added tests for check_model in MarkovModel
added tests for check_model in MarkovModel

sandeepkrjha/pgmpy,anaviltripathi/pgmpy,ankurankan/pgmpy,liquidmetal/pgmpy,yashu-seth/pgmpy,pgmpy/pgmpy,sandeepkrjha/pgmpy,ankurankan/pgmpy,abinashpanda/pgmpy,kris-singh/pgmpy,anaviltripathi/pgmpy,abinashpanda/pgmpy,jhonatanoliveira/pgmpy,kris-singh/pgmpy,jhonatanoliveira/pgmpy,liquidmetal/pgmpy,khalibartan/pgmpy,yashu-seth/pgmpy,pgmpy/pgmpy,khalibartan/pgmpy