Will/optimize ease

* Cache the processed text (tokenized / tagged / stemmed) so it can be re-used for all criteria in a rubric.
* Add a script to benchmark EASE.

This results in about a 63% performance improvement on the benchmark (4.4 seconds down to 1.5 in my VM).

@stephensanchez Please review, but not until after the hackathon :)
Cool approach to benchmarking. If we wanted to continue using this, it may be nice to write this to a delimited file rather than just print statements