ExaProxy 'GitHub' release

This is the first release since our move from Google Code.

Many improvements since 1.1.2 including :

• ICAP mode
• Separate process to manage workers
• Smaller, faster core reactor (only moving data around and with internal IPC API)
• Improvement: automatically pick the best reactor by default
• kqueue reactor on BSD
• exaproxy.http.mask to remove the presence of any previous proxy
• Forked children managed by a dedicated process (as Squid wants to do)