WIP: Benchmarking.
First pass at a benchmarking script.
Use variadic SADD arguments to cut add_to_set times in half.
Rename benchmark.
First pass at moving process to a lua script. Not all the specs are passing.
D'oh, messed up the measure names.
Tweak for easier benchmark comparing.
Only load Lua script for processing items once.
WIP
Implement :union processing technique and support it alongside the standard and lua techniques.
Add a Predictor.processing_technique configuration option to determine how item similarities are processed.
Allow overriding processing_technique on a per-class basis.
Have the :union processing technique respect similarity_limit.
Cover all the different processing techniques in specs.
Tweak processing_technique config method names for consistency.
Don't crash if add_to_set is called with no items.
Update benchmark:process for API change.
Update README with information on Predictor.processing_technique.
README tweaks.
Merge branch 'master' into performance

Conflicts:
	spec/base_spec.rb