Print set read deadline error message.
Always try parent proxy in case of dial error.
Fix response not keep alive by default.
Rename directionConnection to isDirect.
Reset client timeout count upon getting request.
Remove handleClientWriteError.
Do not take special handling on log with debug option.
Use debug log to print parent proxy.
Change default keep-alive value to 15s.
Collect client&server connection count, better debug message.

Some debug messages now contain "client: <remote addr>", we can group debug
message by client by grep and sorting on remote addr.
Script to group log by client.
Print send body debug message with client info.
Fix bug for close connection response with no body.

cow should add content-length: 0 header to indicate the end of close
connection responses with no body, add chunked encoding for those has body.

Safari will wait for body when cow incorrectly adds the chunked header.
As Safari limits number of concurrent connections to the proxy, it will
block on such erroneous responses.
Bump version to 0.7.6
Merge branch 'develop', version 0.7.6