Verify contents and format of track documentation

Each language track has documentation in the `docs/` directory, which gets included on the site
on each track-specific set of pages under [/languages](http://exercism.io/languages).

We've added some general guidelines about how we'd like the track to be documented in exercism/exercism.io#3315
which can be found at https://github.com/exercism/exercism.io/blob/master/docs/writing-track-documentation.md

Please take a moment to look through the documentation about documentation, and make sure that
the track is following these guidelines. Pay particularly close attention to **how to use images**
in the markdown files.

Lastly, if you find that the guidelines are confusing or missing important details, then a pull request
would be greatly appreciated.