Added a regression test for keep-alive chunked POST
Fixed a bug with keep-alive chunked requests

If you make a POST request with 'Connection: Keep-Alive' and use chunked body encoding, tornado will not interpret that as a connection that can be kept alive, and will close the connection.
Merge pull request #1125 from duedil-ltd/chunked-encoding-keep-alive

Fixed a bug with keep-alive chunked requests