Add option preserveMediaQueries to complement removeStyleTags

This adds the option and test coverage to preserve media queries for CSS inside style tags while removing the rest of the styles from the style tag. This is to resolve https://github.com/andrewrk/juice/issues/3

Based on the somewhat scattered state of the test runners, I added the tests where it made sense, so they are run with `node test/run.js` but had to introduce a new path that includes json format options and run through `juice.JuiceContent` instead of just using `juice`. This felt like it set things up best to add additional tests with other options in the future while keeping all existing tests they way were.