[wip] Playground with remote documents, among other things

This weekend, I started working on #339, and got somewhat distracted with adding UI for providing input/context/frame as remote documents. This turned into some rethinking of various things that were happening in the UI, and became a larger set of modifications. So now this is basically a kitchen sink PR, that I feel generally improves the experience, but is not very cohesive as a feature set. I have no problem pulling (certain) individual features out, but some of the things would be harder.

Live demo:
> http://bollwyvl.github.io/json-ld.org/playground-remoteurls/playground/

I am looking for feedback on which of these things are good and/or could be improved, which are not and should be removed, and which need to be reimagined:
- adding remote url/context/frame
  - if an editor is set to remote, it becomes readonly
- adding ability to copy output context from the input context (and optionally keep them linked)
- permalink uses `#` (still accepts `?`)
- permalink moved to top bar
- removing dead theme selector code
- reverting to native `JSON.parse` vs. `jsonlint.parse` until we have a demonstrable need (i.e. error paths from jsonld.js)
- more function docs
- icons all over
  - using the font-awesome 2.3.x EOL release for a few clutch icons not in the version used on the rest of the site)
- whitespace
- linting
- small css changes
- "loading..." message to avoid flash-of-unstyled-content

Thanks!