Rename test.html → demo.html
Initial work on a new demo page.

- Restructured into a directory instead of being a single page.
- New shorter style switcher.
- Redesigned the style list as a side bar.
Subtler detection fail indication.
Removed special tests from demo.
Merge branch 'master' into demo

Conflicts:
	demo/index.html
Extracted export-related scripting to export.js
Merge branch 'master' into demo

Conflicts:
	demo/index.html
Minor fix of HTML markup.
Another post-merge fix.
Draft implementation of category switching and on-demand highlighting.
Merged detection.js + styleswitcher.js into demo.js
'other' category.
Selection 'common' category by default.
Copy background and text color of code into #languages.
Select default style on load.
Remove a local var in category click handler.
Dropped <a> elements from category and style switchers.
First draft of snippet generation.

Missing:

- Language names and categories in the resulting index.html
- Styles and scripts
- Discovering multiple snippets for one language (e.g. XML and
  HTML).
Passing language header info to the demo template.
Removed some repetition in reorderDeps.