Proposed documentation changes for required CEM integration features.

These are just the docs--we still have to actually implement the features!
remove POST /api/submissions/:id/meta.
changed sample review to have a valid _id so tests pass.
implemented new CEM functionality.
added 'mark review as processed' interactive to /demo
changed review.processed field to a date rather than a boolean.
Merge pull request #92 from toolness/cem

Add features needed for CEM site