Update http_parser to 0.6.0 and remove CONNECT request hack

Update http_parser to 0.6.0. Remove the CONNECT request hack due to bug in previous version.

NOTE: The referenced PR for http_parser in the proxy_connection comments has been merged in prior to release version 0.6.0 of http_parser so it is presumed based on the comment that this should work as expected; however, note that there are NO unit tests existing validating the behavior of proxy_connection in an https environment, as far as I could tell.