Disable server side cursors

We're using subquery loading, which makes them useless
(http://docs.sqlalchemy.org/en/rel_0_9/orm/query.html#sqlalchemy.orm.query.Query.yield_per).
Only load columns that contain required values
Commit to Solr after an import
Add tests for _iterate_path_values
Change tox.ini to a working one
Add tests for merge_paths
Add mock to tox.ini
Add tests for _defer_everything_but
Add tests for queue_to_solr
Add tests for _iter_bounds