BUG: Fix floating pt exception in __mod__

By removing the acceleration (fails on Travis CI right now too).
Will investigate in the future.
ENH: Add 'mod' method to frame

NOTE: This is currently *not* accelerated.
ENH: Add truediv, floordiv, & mod to Series

Note that floordiv and mod will not be accelerated right now.
ENH: Add truediv and floordiv methods to panel
DOC: Add new arithmetic methods to docs.
DELETEME: Added verbose messages to expressions