Optionally open a particular notebook on startup.

Pass a name as a parameter --notebook=name and the server will
redirect to /view/:name (urlencoded) after secure login.

Note: csrf.js would not delete the csrf cookie as expected when
loading from a non-root path, which would cause a websocket error;
this is fixed here.
Merge pull request #16 from n8han/master

Optionally open a particular notebook on startup