Fixes #26, #27, and #28

* Fixes requirements in setup.py to follow new guidelines
* Fixes documentation to include package-level docs
* Fixes data query bug that could return fewer results using pattern matching
Fixes issue #30
Finish fixing #30 :/
Added runtime-configured null session support
Fixed docs, updated changelog.
added RestrictError, a test for it, and usage in Model.delete() for it.
Updating failing tests for #36
Merge pull request #35 from pconerly/restrict-error-on-delete

added RestrictError, a test for it, and usage in Model.delete() for it.
Merge pull request #37 from iamkhush/master

Updating failing tests for #36
Added on_delete behavior for OneToMany columns

* Bumped version to 0.27.0
* Added auto-tagging support when pushing a new release
* Fixed round-tripping for objects with nontrivial Redis encodings
* Added warning for non-explicit on_delete behavior
* Added exception for non-explicit on_delete behavior for rom >= 0.28.0
Added multi-column unique constraint, some fixes

* Added composite unique constraints via unique_together attribute
* Fixed issue where rom would leave extra data around for deleted entities
* Added convenience function util.clean_old_index() for cleaning out extra data
  for deleted entities
* Added convenience function util.show_progress() for watching progress of
  util.clean_old_index() and util.refresh_indices()
* Fixed tests should no longer leave testing data in DB 15 (running tests will
  clean out this testing data)
* Fixed bad string docs
Regen docs for upload.
Added on_delete='cascade', query result iterator

* OneToMany columns can now use on_delete='cascade' for cascading deletes,
  closes issue #39
* OneToMany columns can now include a column name on the foreign model to
  allow for multiple references, closes issue #23
* Updated and fixed index cleaning with util.clean_old_index(), now requires
  Lua scripting