CYB-201 - Engagement Index: opt-out students should see the disclaimer too

https://jira.ets.berkeley.edu/jira/browse/CYB-201
CYB-200 - Engagement Index: disclaimer is misleading

https://jira.ets.berkeley.edu/jira/browse/CYB-200
Merge pull request #129 from christianv/CYB-201

CYB-201 - Engagement Index: opt-out students should see the disclaimer too