version to 0.22.0

* Add benchmarking for `FakeRecord` (#146)
* Add missing `Model` unit tests (#150)
* Add `FakeRecord::Attributes` mixin (#118)
* Add `FakeRecord::Associations` mixin (#147)
* Add `FakeRecord::Persistence` mixin (#148)
* Fix `FakeRecord::Associations` mixin (#149)
* Update `FakeRecord` to use mixins (#151)
* Cleanup `TestHelpers` (#153)
* Add `assert_association_saved` (#154)
* `FakeRecord`, seperate "changed" and "saved" attributes (#155)
* Allow manually setting `updated_at` (#156)
* Add `file_name`, `dir_path`, `file_path` to `MR::Factory` (#157)
* `ReadModel`, make `where` and `order` just use `merge` (#159)
* `Model::InvalidError`, set backtrace to caller of `save` (#160)
* Setup for adding a `find` method to `ReadModel` (#161)
* Add `find` method to `ReadModel` (#162)
* `FakeRecord` use AR default timezone for timestamps (#163)
* Remove NsOptions as a dependency (#164)
* Use latest Assert to run tests in DB transactions (#165)
* `assert_association_saved` use actual record's class (#167)
* `ReadModel` querying, keep expressions ordered via array (#166)

/cc @kellyredding