v0.2.1

* Added support for js expression in the `from` node addressing issue #86
* Enhanced `JoinReferenceNode` performance in the default assert case where there are no `references` to left or right context.
* Added ability to use `or` and `not` in tandem to check for the non-existence of multiple facts. #85
* Fixed issue with `from` node where an undefined property would be tested. #89
* You can now define a custom resolution strategy.
* Compiling nools files now supports the from modifier.
* Documentation updates
   * Updates about from node support with js values.
   * New documentation about using `or` and `not` constratints together.
   * Updated `or` documentation to include a three constraint example.