Added ZeroDivisionError to float division.
Merge remote-tracking branch 'upstream/master'
Fixed broken math functions that return bool and added some more.
Added exception hierarchy except for OSError and UnicodeError (requires arguments). Comment out the errors that aren't needed if memory becomes an issue.
Fixed modulo operator on ints and mp ints to agree with python. Added intdivmod.c and tests/basics/modulo.py.
Fixed floor division on mp ints and small ints. Added a floordivide test case.
Merge pull request #359 from rjdowdall/master

Fixed some math functions and added more exceptions.