added support for typeable URL in consent form (closes #29)

Removed password from the old consent URL (giving consent does not require password).
Also shortened the URL for the typeable version. This will be backward-compatible with the old clients (both URLs work). This will close #29.
@ben-jones, can you please review this?
I understand that we are trying to get this as concise as possible, but I'm not sure that a character variable is necessary. Flask lets you include variables in the URL, i.e. app.route("/consent/<username>"), so it may be better to do a portion of the URL in place of a parameter. Please respond below and let me know how you feel. Also, see http://flask.pocoo.org/docs/0.10/quickstart/#variable-rules for more details about the variable path thing.