Does not handle HTTP informational responses correctly

[daguej]

httpie incorrectly treats informational responses (102-199) as a final response, printing the response headers and exiting.

$ http :5000/102
HTTP/1.1 102 Processing


$

Compare to what actually happens:

$ nc 127.0.0.1 5000
GET /102 HTTP/1.1

HTTP/1.1 102 Processing

HTTP/1.1 200 OK
…

httpie should print the zero or more informational responses (if response headers are enabled) before printing the final response and exiting.