Prevent Rosetta Flash attack

Refer to http://miki.it/blog/2014/7/8/abusing-jsonp-with-rosetta-flash/ for a description of the vulnerability. This simple patch prevents the attack from working.
Update tests for Rosetta Flash vuln patch
Correct jsonp_spec content-lengths
Merge pull request #16 from valverde/patch-1

Prevent Rosetta Flash attack