Updated .travis.yml.
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.
Fixed test models for python3.x
Added exclusion filters support
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
Updated docs for generic view from "filter_class" to "filterset_class" as expected.
When creating a new filter set iterate the filters and apply the parent attribute so the field has a reference to the viewset
Add MethodFilter which will allow for action to be a string and call a class method of the filterset it exists within
* Documentation for the method filter
Tests for the method filter
Use six iteritems to be compatable with python3
Use six to determine the proper text types, unicode no longer exists in python 3
Fixes a bug with python 2.6 deepcoy, see http://bugs.python.org/issue1515
Wrong copy import
Fix some formatting in docs.

The indentation was causing the whole block to render as a `<pre>`.
Merge pull request #122 from meshy/patch-1

Fix some formatting in docs.
Merge pull request #120 from Ogreman/patch-1

Updated docs for generic view from "filter_class" to "filterset_class" as expected.