Adds a manage.py script to assign reviewers to talks.

Requires that a 'reviewers' group exist, and that there are people assigned to it (otherwise it won't find any reviewers to add!).

It will assign up to 3 reviewers, where those reviewers are NOT one of the speakers, and that reviewer has not opted out of reviewing that talk.
Makes the reviews UI legible.

Some bootstrap tab things were being co-oped by our header styles.
Makes the list of review assignments legible, by providing and actual table border and removing the unused column.
Adds "todo" about shuffling the list of reviewers.
Chooses reviewers randomly, from those who have the fewest assignments.
Merge pull request #87 from pyconca/review-assignments

Adds a manage.py script to assign reviewers to talks.