Test for ExaminePage, fix two bugs it found.

This constructs `/contigs`, `/spec` and `/genotypes` responses from a VCF file.

The two bugs were:

  1. The initial request for `/genotypes` was being throttled, which artificially slowed page load by 500ms.
  1. The exploded rows from multiple samples were being dropped.

I also deleted some code that wasn't being used to boost our code coverage. I suspect that if/when we revive this code, it will be substantially different. So deleting is not a big loss. But feel free to disagree.

This PR bumps our test coverage from 25%→[53%](https://coveralls.io/r/hammerlab/cycledash).
It's true, but if's impossible that it will fall out of sync without you noticing, since the tests will fail!

This is definitely a tradeoff with testing—it does create more overhead when you make API changes, but I'd argue strongly that it's worth it in the end. The test changes makes it quite clear exactly what you're changing.