Improve parse performance drastically (45x faster). closes #4

 - by having less keys on each token the recursion is faster.
 - avoid unnecessary work on the WhiteSpace token creation.
 - Esprima is also around 25% faster with loc:false.
 - Also replaced some `Array#forEach` and `for in` with plain/faster loops.
 - Add perf tests to make sure we don't degrade it too much in future updates.
improve `moonwalk` performance drastically (110x). see #4

the sorted insert was very expensive so we used a faster approach.
bump version to 0.2.3 and update readme