Fix bug in review_section

/2014/reviews/section/talks/ and similar pages were not showing all
the proposals they should have, due to a bug in the review_section
view.

Also changed the review_assignments view to grant access to all
superusers, for consistency with other views.

Also added some doc about how to enable proposal submission, and
added a couple help text strings for the date fields that control
the dates submissions are open, and fixed a bunch of PEP-8
problems.
Don't focus on markedit input fields
Merge pull request #43 from caktus/feature/review-section-bug

Fix bug in review_section
Merge pull request #44 from caktus/feature/markedit-focus-bug

New proposal pages immediately scroll down
Refs #45: Add domain level field to talks
Update display of levels on proposal detail page
Remove domain_level from all but tutorials.
Merge branch 'feature/45-audience-level' of github.com:caktus/pycon into feature/45-audience-level

Conflicts:
	pycon/models.py
	symposion/templates/proposals/_proposal_fields.html