[auto-link-css] Added a .feature describing auto-link-css
[auto-link-css] Implemented auto linking of .css

See the feature for an explanation.

Notes:

* The scope that's available at ERB render time is more powerful now.

* The general idea is to use this scope as a bridge between things
  like (1) the file system and (2) general configuration while
  rendering.
CSS can now easily be added to a presentation

Merge branch 'auto-link-css' into upcoming

* auto-link-css:
  [auto-link-css] Implemented auto linking of .css
  [auto-link-css] Added a .feature describing auto-link-css