Implemented support for flow selection via Route header

Signed-off-by: Kirill Mikhailov <kirill.mikhailov@gmail.com>
Implemented Websocket server transport

Signed-off-by: Kirill Mikhailov <kirill.mikhailov@gmail.com>
Added extension parameter sip.makeResponse

Signed-off-by: Kirill Mikhailov <kirill.mikhailov@gmail.com>
proxy.js: fixed CANCEL request route handling

Signed-off-by: Kirill Mikhailov <kirill.mikhailov@gmail.com>
changed parser to parse AOR uris in 'Route', 'Record-Route' and 'Path' headers

Signed-off-by: Kirill Mikhailov <kirill.mikhailov@gmail.com>
Return right reason (430) in case of failed flow

Signed-off-by: Kirill Mikhailov <kirill.mikhailov@gmail.com>
Added simple example of websocket enabled proxy (examples/websocket-proxy.js)

Signed-off-by: Kirill Mikhailov <kirill.mikhailov@gmail.com>