Fix directive in fixtures
Add strict mode

Opt into 'strict mode' with the following comment at the top of a CSS
file:

/** @define ComponentName; use strict */

Strict mode will disallow *any* class names that don't match the defined
ComponentName. For example, `.ComponentName .Another` would fail in
strict mode.

This changeset also includes more accurate detection of conformance to
the SUIT CSS naming conventions.

Fix gh-2
Fix gh-6
Refactor tests
Update CHANGELOG