1.6.0

A new series with improvements in the HTTP client and server.
Broadly compatible with the 1.5 series with exception of headers definitions and actors
based on multiprocessing module (both have been removed because not used).
This version brings a critical bug fix for HTTP responses with non standard
values in body or content headers

• New is_message_complete method in HttpResponse
• Critical bug fix for HTTP response with body when they should not have it.
  Disregard the body and content headers #257
• If http-request module is installed, use its C parser as default HTTP parser.
  The python parser can still be used by passing --http-py-parser flag in the command line
• Removed headers definitions, no longer used #222
• Removed actors based on multiprocessing module, not needed a9cc662
• Tests run with both python and C http-parser
• Fully compatible with python 3.5 & 3.6