mitmproxy/todo

This is a loose collection of todo items, in case someone else wants to start
hacking on mitmproxy. Drop me a line (aldo@corte.si) if you want to tackle any
of these and need some pointers.

Features:

    - Add some "workspace" features to mitmproxy:
        - Flow comments
        - Copying/duplicating flows
        - Ordering by time, size, etc. a-la-mutt (o keyboard shorcut is reserved for this)
    - Upstream proxy support.
    - Support HTTP Digest authentication through the stickyauth option. We'll
    have to save the server nonce, and recalculate the hashes for each request.
    - Chunked encoding support for requests (we already support it for responses).
    - A progress indicator for large files