Benchmark of faster version of Hash#reject.

gistfile1.txt

graham-battys-macbook:rubinius-master graham (perf-hash)$ bin/rbx benchmark/bin/benchmark -tx -tr benchmark/core/hash/bench_reject.rb
=== bin/rbx ===
       reject string    91940.6 (±14.1%) i/s -     445500 in   5.020721s (cycle=2750)
      reject numbers   220166.2 (±7.9%) i/s -    1092648 in   4.999565s (cycle=10308)
      reject! string    94992.6 (±7.4%) i/s -     476934 in   5.052189s (cycle=5482)
     reject! numbers   199148.9 (±6.9%) i/s -     995456 in   5.025582s (cycle=11312)
=== ruby ===
       reject string    51115.8 (±12.1%) i/s -     252488 in   5.011600s (cycle=3412)
      reject numbers    63331.0 (±12.9%) i/s -     311360 in   5.005070s (cycle=3892)
      reject! string    98969.8 (±11.5%) i/s -     492195 in   5.039376s (cycle=5181)
     reject! numbers   221659.9 (±20.0%) i/s -    1072786 in   5.028255s (cycle=7502)