Velociwrapper

- bugfix to make VWCollection extend object

- reverted _create_search_params() change. Search parameters stay. Broke
too much stuff.
- added clear_previous_search() to clear the search and reuse the
collection

- Calls to _create_search_params() create the native parameters to send to
elastic search and then remove the settings from the object. This allows
the collection object to be used for a new search. The drawback is
subsequent calls to all() will not work as expected.
- added functionality for one() to return the first result of a query
- Raises AttributeError if an attribute doesn't exist (previously returned
None but we have now considered this a bug)
- Fixed bugs related to _set_by_query not being set
- Fixed _deleted not getting set
- Added relationship functionality
- relationships can be specified on single columns
- setting of a model on a relationship attribute does not yet work

- Fixed deepcopy of shared resources (specifically self._es)

- Fixed issues with pagination
- Fixed issue where some values were not copied

- MOAR bug fixes