Measure perf for node-sass after conversion

[aruneshchandra]

[boingoing]

Node-sass-napi binary built from boingoing/node-sass@b663dcf
Node-sass-nan binary built from sass/node-sass@cc7c3b3
Node-V8 8.x built from 75e28c5

Performance is measured via this suite:
https://github.com/eoneill/node-sass-perf-test

The performance test doesn't drill-down into specific areas or APIs to give details on what is taking up the time, we just have an overall execution time.

node-sass Nan on V8-Node 8.x	node-sass NAPI on V8-Node-Napi 8.x
12ms	13ms
12ms	14ms
13ms	12ms
12ms	17ms
13ms	13ms
17ms	12ms
13ms	15ms
12ms	12ms
12ms	12ms
12ms	12ms
24ms	12ms
11ms	12ms
13ms	24ms
15ms	13ms
13ms	13ms
12ms	12ms
13ms	15ms
11ms	12ms
12ms	12ms
12ms	12ms
avg = 13.2ms	avg = 13.45ms (+1.9%)

Tests run on a Windows machine with this hardware:
Intel Xeon E5-1620 v3 @ 3.50GHz
16GB DDR4 @ 2133MHz
Samsung XP941 SSD