added rate limiting options

[GlenTiki]

Boom! No change in perf.

Glens-MacBook-Pro-2:autocannon glen$ ./autocannon.js -c 1000 -d 30 http://localhost:3000
Running 30s test @ http://localhost:3000
1000 connections

Stat         Avg     Stdev     Max
Latency (ms) 51.7    18.15     631
Req/Sec      19183.6 1286.36   20975
Bytes/Sec    2.13 MB 144.66 kB 2.36 MB

575k requests in 30s, 63.88 MB read
6 errors (0 timeouts)

Fixes #27

Example usage:

Glens-MacBook-Pro-2:autocannon glen$ ./autocannon.js -R 10 -c 2 -a 100 http://localhost:3000
Running 100 requests test @ http://localhost:3000
2 connections

Stat         Avg     Stdev    Max
Latency (ms) 0.4     1.77     12
Req/Sec      10      2.24     15
Bytes/Sec    1.12 kB 254.04 B 1.73 kB

100 requests in 10s, 11.1 kB read

[mcollina]

LGTM @davidmarkclements?

[davidmarkclements]

this is really cool

my only thing is - I'd like to review the entire API - but that's another exercise, happy for merge

[GlenTiki]

Merging, lets open an issue for API review. 👍