Start on a condense branch. This is related to #20

See https://gist.github.com/4329932 for more detail.
Rewrite filterset in more vanilla-javascript style, add more tests
Move .is to prototype, start testing quoteds
Simplify style.js
Cleanup
Profile and optimize reference lookups
Merge and fix renderer optimization'
Update chunker to less.js's version. Fixes #184
Add oneline test
Simplify filter system, support numeric variables in filters
Add filterset.eval, support variable filter combinations.
Add field test
Add filter test
Simplify, use lodash where possible
Remove straggling import stuff
Optimize fontset detection
Allow for filters which compare fields.
Update filtervariable test
Rewrite zoom filters as objects, support variables in zoom definitions.
Revert "Update chunker to less.js's version. Fixes #184"

This reverts commit 78b3a5a5d4371462e48094e59b427da8a4b9ed56.