Include runtime stats in report

Created by: dnyrop

Would it be possible to include the runtime stats in the reports ?

 [~] Audited x page snapshots.
 [~] Audit limited to a max of x pages.

 [~] Duration: xx:xx:xx
 [~] Processed xxx/xxx HTTP requests.
 [~] -- xx.xxx requests/second.
 [~] Processed xx/xx browser jobs.
 [~] -- xx.xxx second/job.

 [~] Burst response time sum     x.xxx seconds
 [~] Burst response count        xxx
 [~] Burst average response time x.xx seconds
 [~] Burst average               xx.xx requests/second
 [~] Timed-out requests          xx
 [~] Original max concurrency    xx
 [~] Throttled max concurrency   xx

This is very useful information, but unfortunately only available in the terminal output at the moment. It seems like a good idea to include this in the metrics module.