CLN/TST remove compat.scipy

re-branch of https://github.com/pydata/pandas/pull/7253#issue-34432164

-Move ``percentileofscore`` to ``stats.misc``; Update ``percentileRank`` to reflect the move.
-Change testing references to ``compat.scipy.rankdata()`` , to use ``scipy.stats.rankdata`` directly
-Delete compat.scipy