Add welcome page.
Fix user token acceptance test.

The page content didn't include the pre-filled input field
so have to explicitly check using a CSS selector.
Resize headers.
Extract CSS color to another stylesheet.
Toggle user token.
Combine links for a challenge to one area of page.
Preserve directory structure of submission.

* When extracting a submission archive it will record files
  in directories.
Specify type for search query.
Merge pull request #24 from atsheehan/preserve_dirs

Preserve dirs