Make zoom controls more granular
Gracefully handle less-than-perfect unit state data.
Merge pull request #639 from makyo/zoom-slider-1

Make zoom controls more granular

This is a small fix to ease some of Jorge's woes with zoom; there will be future work around fitting the visualization to the window.
Merge pull request #640 from kadams54/fix-js-errors-1388465

Gracefully handle imperfect unit state data.

When inspecting units for errors, we need to be able to deal with malformed or missing data returned from the API. We already know an error condition exists, so there's no guarantee things will be as they should. Inspect as many fields as possible to determine if there's a relation error. Don't assume a field is actually present; if it isn't, move on.