generates the equivalent curl command of the request

Here is a pull request which adds a curl button next to the send button.

The curl button will simply give the equivalent curl command of the resolved request where the user can copy the the text and execute the curl command.

I had to refactor request.js#send method into several inner methods which generates the headers, url, etc. 

However, I haven't tested the OAuth feature and the Basic Authentication feature. Would you by any chance help me do a sanity check as well?

Is there a comprehensive test suite that can be run? I see selenium and jasmine tests. What is the status of those test suites?

Best Wishes,
neowulf33