GoogleChrome/experience-sampling — pull request #24 by adrifelt (2014-10-15 01:12:26+00:00)
Title: Support optional dropdowns

This gives a "blank" answer for dropdowns that are optional.

![screen shot 2014-10-14 at 6 11 10 pm](https://cloud.githubusercontent.com/assets/4962198/4639186/5215dfbc-5408-11e4-8c07-054095e985b1.png)