Released gnet v1.5.0

#Features

• Move the logging module out of the internal package and refactor to make it serviceable for users d56606 b6b1cf 8837a9

#Enhancements

• Support writev and readv in eventloop f299a8
• Reduce GC pause frequency for Conn.AsyncWrite (#218) 477bb4
• Improve logging module 8837a9 b6b1cf
• Refactor the inside AsyncTaskQueue to make it more generic 2d1a46
• Reduce GC pause frequency for accepting connections 2d1a46

#Docs

• Add a new user case: Tencent Games b7ea83
• Add a new donor ee965a

#Misc

• Add debugging log when error occurs in Accept() #222
• Make some trivial changes to ring-buffer 1bdd3a