Fix error in util helper methods.
Fix error in util helper methods.

fixes error with checking if something is iterable. Before class methods
would cause it to return true. Now we check if it is a class as well.

Adds method for checking if something is a mapping

joaander/hoomd-blue,joaander/hoomd-blue,joaander/hoomd-blue,joaander/hoomd-blue,joaander/hoomd-blue,joaander/hoomd-blue