Flatten - optional

Hey @robmckinnon 

what do you think of this change: I've added '/download?flatten=false' as an optional parameter. When it's supplied, the PDFs don't get flattened so the test can still run as before.

I'm a bit uncertain if I'm supplying that parameter in the right places within the test suite. So if you could verify that, I'd be grateful.

I've already modified the Clojure CLI app to take that argument as well as the Clojure web service and not flatten the PDF if the argument is set to 'false'.

Thanks