Upgrade to pegJS 0.8

Featuring an approximately **90%** reduction in template compile time. Zomg-we're-faster-than-Handlebars. All tests pass. Node 0.8 compatible.

    pegjs-0.7$ time bin/dustc ~/Desktop/syntax.md.txt > /dev/null

    real	0m1.119s
    user	0m1.100s
    sys	0m0.024s

    pegjs-0.8$ time bin/dustc ~/Desktop/syntax.md.txt > /dev/null

    real	0m0.114s
    user	0m0.096s
    sys	0m0.017s

Upstream changes that affect us:
 - line and column variables are now functions
 - parser.toSource() removed in favor of a generator option that switches between an object and string versions