Add --cache flag to pegjs compiler. Refs #16

Early results show that this makes the tracer branch just
as fast as the master branch. The only tradeoff is that it
currently adds an additional 150kB to the minified file size.

Author: nwronski

Gruntfile.js

@@ -104,7 +104,7 @@ module.exports = function(grunt) {
         options: {
           failOnError: true
         },
-        command: './node_modules/.bin/pegjs --trace -e parser src/grammar.pegjs .tmp/parser.js'
+        command: './node_modules/.bin/pegjs --cache --optimize speed --trace -e parser src/grammar.pegjs .tmp/parser.js'
       },
       test: {
         options: {