"UTF-*" misspelling and new response attribute from Mandrill

I started getting exceptions inside my app because Mandrill had added a new attribute to their responses, "reject_reason". So this pull request has a fix for that.

When I pulled and got the latest changes though, I found that I was getting another crash, and it turns out that "UTF-8" was spelt "UFT-8", leading to IOExceptions being thrown. So I fixed that up in this pull request too :-)

Cheers, 
Martin