Add an /analytics page

[ondrae]

Description

We've done some great work on the issue finder analytics over at https://github.com/codeforamerica/gotissues

We should merge the easy to set up parts into this main repo. That way, if another group were to use this project, they'd get all these built in analytics too.

How

• [x] Add a route for /analytics
• [ ] Write instructions for using your own GAnalytics code in the template
• [x] Copy over all the GAnalytics code from https://github.com/codeforamerica/gotissues, everything that doesn't require a database.