Refactor code and workaround for saml-auth-response -1

[esuarezsantana]

I needed to add a feature but the source was hard for me to read, so I rewrote it.

I have kept the args interface and the functionality, except for:

• Just require last versions of Gtk and WebKit2.
• Use logging module and reduce verbosity levels.

Maybe not worthy enough to merge, but worthy enough to have a look.