Use periods instead of colons after question numbers.

[#49854337]

https://www.pivotaltracker.com/story/show/49854337
Enforce singular answers for MC in summary

I wasn't able to duplicate [#49081933], so I'm not at all sure what's causing it, but in the event that there are multiple answers recorded for a multiple-choice question without multi-answer checked, only the last one will be shown.

https://www.pivotaltracker.com/story/show/49081933
View spec for activity summary (and a bug fix it revealed)