Add support for program committee team

[tylerdave]

Add support for program committee team members to be able to rate / review talks and then view full proposals (w/ speaker info) after feedback period is over.

[befreeman]

PR #34 should add the committee team to fixtures, but I don't know if we already have a permission configured which will allow the team to see the speaker info.

[tylerdave]

There's not a permission for this yet but we could either add one to the symposion fork or/and add dates or a setting for phase two of the review process. Let's discuss.

[tylerdave]

I've added an "Organizers" group for now in production. It's probably ok to put everyone on the organizing committee in that group. If we find we need some program-committee-specific behavior we can add a group for that later.