cow chain client side done.
refactor listen format in config similarly
Merge pull request #95 from styx-hy/feature/cow-chain

Refactor listen format in config
Update sample rc.

- Introduce the new cow protocol server
- New syntax to specify proxy server address in PAC
Refactor proxy server representation.
Fix proxy config upgrade bug.
cow chain server done.
Upgrade config for listen directive.
Fix CONNECT bug.
Always keep cow connection alive for more reuse.
Kill server upon INT/TERM signal in test script.
Merge branch 'feature/cow-chain' into develop
Show host name in error page.
Fix using multiplexing connection for direct site.
Fix keeping cow connection alive.
Fix conn_pool test, not covering multiplex channel.
Do not retry if there's no parent proxy.
Fix AsDirect returns false for new site.
Fix test as new site is consider as direct now.
Allow client use basic authentication.