Add monitoring plots

[drJAGartner]

We need to be able to understand problems more quickly. I would like it if we add a set of simple plots to a 'Social Media Diagnostics' page, which can start with the following plots:

• [ ] Number of tweets ingested in a fixed period (~30 m) vs time
• [ ] Average time interval between the tweet creation time and receiving the tweet
• [ ] Number of posts clusters made in a given time interval
• [ ] Number of events made per day

We may expand this selection, but I think that this subset will give us the ability to pretty quickly diagnose problems like the ones we're seeing now.

[lukewendling]

visit :3004 on xdata prod server for related visuals.

app code currently lives at github.com/lukewendling/go-pinger