Made changes recognize list of OpenID providers.
1. Changed config.py to add an array of OpenID providers, with their links.
2. Changed views.py to add a providers kwarg to render_template in login().
3. Changed the login.html template significantly. It now has a javascript function that prompts for the username and then composes the OpenID. The providers are looped through and the function is kept as an anchor for each provider name.