Python 3 Compatability

[baxelrod-bdai]

I believe this one-line change (plus an added import) is all that is required for Python3 compatability. The second to last line in the Collection class is the only change, but it requires the collections module.

import collections
...
class _Collection(_Call):
    """Base class to expose entities methods to main object."""
    def __init__(self,entities=[]):
        self.entities=copy.copy(entities)
        #link entities methods to drawing
        for attr in dir(self.entities):
            if attr[0]!='_':
                attrObject=getattr(self.entities,attr)
                if isinstance(attrObject, collections.Callable):
                    setattr(self,attr,attrObject)