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).
The difference between these two methods isn't too clear from the names! I remember being unclear between the two when I was doing a RecordStore read-through.

I realize we don't want a super long name for a method that's called a bunch of places, but I'm still putting in a vote for `updateGenotypesThrottled`.