Fix issue #115

Moved "bailout" code to the top of the Filter.filter method, so it catches empty list and tuple.
Ammended my fix for #115

Instead of moving bailout code, added condition on list length, to prevent unpacking of empty list.
Address passing lookup type to tilter method.

LookupTypeField.compress() now returns Lookup (a simple namedtuple) instance.
Filter.filter() now checks for value being a Lookup instance and handles setting lookup_type
Adjust tests to handle these changes.

Fixes: #115
Fix typo in LookupTypeField.compress.
Merge pull request #116 from augonis/develop

Fix issue #115