Hooked up Engagement Index with API

https://jira.ets.berkeley.edu/jira/browse/CYB-82

PR crucial for today's meeting

Hooked up @richcreationsrc Engagement Index with DataCulture's API
DataCultures can query it's DB and bring relevant information to Engagement Index
This properly belongs in the api/v1 namespace; it is responding to a front-end JS request, not a so-called 'normal' rails HTML request.   It is sending data for the code to use, not a human to read.