FIX multiple issues in the newly added partial_fit tests.
ENH Added name_filter for all_estimators function and tests for the same
ENH Added function to handle the validation of y with classes.
FIX Raise ValueError when y does not match with classes arg in pfit
PEP8 autopep8 fixes for the tests directory and estimator_checks file.
MAINT Remove the classes arg test since general tests are introduced
FIX Remove blank lines before docstring introduced by autopep8