[Release] 1.1.1

bug fixes
 - Avoid to close the already closed socket
 - Skip proxy request when destination node is down
 - Fix the resource leaks of socket in server
 - Fix some compile warnings
 - Fix some race conditions in thread.cc
 - Check dynamic_cast result
 - Fix pthread_cond_wait() in zookeeper_lock::_assure_session_connected()
 - Add initialization of cluster#node
 - Remove some deadcode
 - Add null check before the code with the potential null access
 - Exit when IO-buffer is unsafe
 - Fix memory leak of proxy in op_parser_text
Merge pull request #68 from gree/release-1.1

[Release] 1.1.1
Merge branch 'master' into develop