Small docs style fixes in inheritance.rst
Small docs style fixes in inheritance.rst

Change-Id: I01d217cf1a8a1a8791e3b44167dfc4d6a0c77cdb
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/445

sqlalchemy/sqlalchemy,zzzeek/sqlalchemy,wujuguang/sqlalchemy,monetate/sqlalchemy,wujuguang/sqlalchemy,monetate/sqlalchemy,j5int/sqlalchemy,graingert/sqlalchemy,graingert/sqlalchemy,j5int/sqlalchemy