Velociwrapper

- Fixed bug that prevented "not" working in filters
- Fixed a typo that crashed filters with not

- Updated multi_match() to accept additional arguments for ES
- Removed an unused connection that was created in the config.py
- Ensure that the config option "connection_params" is actually passed to
connections (it wasn't always used previously)
- Fixed a bug that prevented "not" condition working in filter_by()

- Fixed a typo in collection.delete()

- Changed VWCollection().delete() to work in more recent versions of
ElasticSearch where delete_by_query() has been removed.
- Changed ESType.prop_dict() to support nested ESTypes (prop_dict() is
called again to create a complete mapping. This works great for using the
`fields` keyword which allows for multifield functionality)
- Fix for some parse errors in the README.rst file
- clarified use of `collection()` in the documentation
- Added documentation for VWCollection.results

- mapper incorrectly tried to put a new alias on reindex even if no alias
was specified.
- mapper now raises MapperError if an alias_name is specified on reindex
but the alias already exists and remap_alias is False/None

- fixed filter_by() using terms:{} on an analyzed field when passed a list