Send WS handshake using event loop instead of write(2)
Send WS handshake using event loop instead of write(2)

ws_handshake_reply was sending its response using a single write(2) call
without error-checking, which could well send only part of it and leave
the client hanging. This change creates an HTTP response object and
schedules it for writing using the event loop.

Tested with Valgrind, no memory is leaked.

nicolasff/webdis,nicolasff/webdis,nicolasff/webdis,nicolasff/webdis,nicolasff/webdis