Add to curl to summary

When debugging an error, it's often very useful to use `curl` to try and reproduce the error against prod, staging or local environment. 

The idea here is borrowed from chrome developer toolbar where you have a "Copy to cURL" context menu.

For simplicity sake, i just added it to the summary as plaintext, but this is totally open for discussion:

![screen shot 2014-05-21 at 21 32 51](https://cloud.githubusercontent.com/assets/48745/3048915/a21c5ace-e151-11e3-8359-e398db5b5c11.png)

This example is very simple, it get's more interesting when all request-headers, cookies etc are added.