Callback for Mandril Handler

The following code can be used to silence the curl response. It also allows you to pass in a call back function which can then be used to process the response from mandrill. 
We were using this project in a website and upon sending an email to mandrill, the response was being echoed out on our site. 
I think in that case I'll change my code back to the original version to keep it backward compatible.  (I'll just fix up the styling)