rezzza/tk1-contexts — pull request #20 by gmorel (2014-12-31 14:43:57+00:00)
Title: Benchmarking - Add http error check

In case of the application is set to run 20 times with a Behat step similar to this:

```gherkin
When I send 20 GET request to "/v2/resource.json" with 0.95 percentile
```

This might be interesting to check if one response is a Fatal Error just to make sure stress test is reliable.

Final result will be like this :

```cli
GET http://api.com//v2/resource.json : 20 calls
total time = 327.893 ms
total time = 397.184 ms
total time = 326.69 ms
total time = 324.644 ms
total time = 414.552 ms
total time = 334.16 ms
total time = 335.416 ms
total time = 411.053 ms
total time = 324.608 ms
total time = 420.223 ms
total time = 337.478 ms
total time = 348.568 ms
total time = 424.103 ms
total time = 348.053 ms
total time = 345.922 ms
total time = 418.029 ms
total time = 327.574 ms
total time = 351.483 ms
total time = 473.734 ms
total time = 347.582 ms
--- statistics ---
results filter on 0.95 percentile
min/avg/max = 324.608/354.17/418.029 ms
with 0/20 HTTP errors.
```

@tyx Need review