Added dfilatov-vow promises into benchmark

We are using dfilatov-vow promises and I wanted to check, how fast they are, compared to bluebird. This is result I got:

```
results for 10000 parallel executions, 1 ms per I/O op

file                                 time(ms)  memory(MB)
callbacks-baseline.js                     315       35.09
promises-bluebird.js                      477       52.71
promises-obvious-kew.js                  1121       81.57
callbacks-caolan-async-waterfall.js      1456       57.82
promises-tildeio-rsvp.js                 2065       94.61
promises-medikoo-deferred.js             3344      207.61
promises-dfilatov-vow.js                 4874      253.87
promises-cujojs-when.js                  8474      179.49
promises-calvinmetcalf-liar.js          11817      231.20
promises-kriskowal-q.js                 17683      483.66
promises-bluebird-generator.js            OOM         OOM

Platform info:
Darwin 12.5.0 x64
Node.JS 0.10.24
V8 3.14.5.9
Intel(R) Core(TM) i7-3667U CPU @ 2.00GHz × 4

results for 10000 parallel executions, 1 ms per I/O op

file                                time(ms)  memory(MB)
callbacks-baseline.js                    305       50.29
promises-bluebird.js                     675      132.02
callbacks-caolan-async-parallel.js      1879      198.16
promises-obvious-kew.js                 4455      695.70
promises-medikoo-deferred.js            7262      515.01
promises-tildeio-rsvp.js               16335      582.99
promises-calvinmetcalf-liar.js        241996     1368.18
promises-bluebird-generator.js           OOM         OOM
promises-dfilatov-vow.js                 OOM         OOM

Platform info:
Darwin 12.5.0 x64
Node.JS 0.10.24
V8 3.14.5.9
Intel(R) Core(TM) i7-3667U CPU @ 2.00GHz × 4
```

Could you quick-check benchmarks? I really doubt about how I patched them.