Add a new reload event, which is dispatched when a reload is required.
This will allow the app to take care of any necessary cleanup/logging.
Merge pull request #51 from DavidCPhillips/master

Add a new reload event, to help apps track forced reloads.
Refactor to unify spf.net.script and spf.net.style.

Moves common code from spf.net.script and spf.net.style into spf.net.resource.
Reduces duplication and enforces consistency between the script and style
execution/loading models.

Progress on #25.