Revert "add proxy_chain, a multi proxies chaining in the same thread feature"

This reverts commit bc7441f5176589ad9a34dc2bde6b91d78a44e3e0.
Revert "add a proxy hook"

This reverts commit 9ae6a91fadb96fd48038fde04cc3d4b61b49a8a1.
fix revert
Merge pull request #891 from lalebarde/master

Reverse zmq_proxy_chain and zmq_proxy_hook