Assets precompilation benchmark

benchmarks

See https://github.com/pmahoney/assets_comp_perf

rails 3.2.9, hike 1.2.1, sprockets 2.2.2

* denotes best time

Ruby 1.9.3-p194

    $ time bundle exec rake assets:clean assets:precompile

    original       hike-patch       all-patch
     42.325         37.600*          37.378
     38.998         38.557           38.250
     38.022*        37.799           37.126
     38.202         37.974           37.459
     38.960         37.754           36.970*

    $ time bundle exec rake assets:precompile

    original       hike-patch       all-patch
     36.427*        37.506           36.078
     37.303         36.241*          35.519
     38.029         36.858           35.859
     37.678         36.733           35.141*
     37.097         37.033           35.856

JRuby 1.7.1

    $ time jruby -G -Xlaunch.inproc=true -S rake assets:clean assets:precompile

    original       hike-patch       all-patch
     62.766*        64.230           56.140
     65.148         64.390           55.848
     64.317         64.083           55.555
     63.633         66.214           55.307
     67.281         63.516*          55.270*

    $ time jruby -G -Xlaunch.inproc=true -S rake assets:precompile

    original       hike-patch       all-patch
     59.819*        60.313           53.250
     61.390         60.454           54.351
     60.377         63.207           52.943*
     62.344         60.622           54.771
     60.040         60.283*          53.624

hike-patch may be in the noise (or a slight negative effect)
for JRuby in this particular test case.  It does seem to have
a small speedup for Ruby 1.9.3.