Inject params for cURL commands

[franroaxeridia]

Hi there! really cool plugin! I wonder if you are thinking about making it possible to add params to the curl command like "--insecure", to work

[gorillamoe]

Great enhancement. I'll add it later on.

[gorillamoe]

The first version of this will add globally added flags via the options table in the setup function.

Once we finished #18, we can also add them on a per request basis.