v0.3.0

Features:

• #3 Remove Timestamp parameter from MessageCallback

Bug fix:

• #5 Fix EventLoop::QueueInLoop bug
• #7 Fix Crush when TCPClient connect failed bug
• #9 Fix Connector::Cancel crush
• #10 Fix Connector was not released bug
• #11 Unit test failed testTCPClientDisconnectImmediately
• #12 testDNSResolver may hang there sometimes
• #13 Wrong usage of struct evhttp_request in trace log
• #14 DNSResolver::OnTimeout do not clear the timer
• #15 testHTTPServer1 may hang there sometimes