Test cleanup

I've been poking around the tests lately, girding my loins for middleware-izing the stale PR https://github.com/rgrove/combohandler/pull/6 I made a year ago and another thing we want at Zillow, and I just couldn't stop my pesky habit of cleaning things that aren't noticeably dirty.

For the most part, the changes are for greater stylistic consistency. The routes tested by the `url rewrites` block should be described there, just like they are in the `config: maxAge` block. `assert.ifError(err)` is more concise than `assert.equal(err, null)`, since we're asserting that the callback did not error. And so on.

I also quieted the jshint errors, because I am a compulsive linter. :rabbit: