Unable to set different CDN with `$.reel.cdn`

Support issue #121 surfaced a fundamental problem with `$.reel.cdn` - it can not be customized. Paths to CDN-served resources are being resolved at the load time and are cached into local vars. That means any consequent `$.reel.cdn` changes hav no effect as the paths have already been resolved.

**The CDN path insertion must not be pre-processed and must happen on the fly.**
