Ability to set the editor content
First pass at hiding JS dependencies from implementation

Create script tags dynamically inside the constructor, pulling the ACE JavaScript libraries
from the relative package path.

Don't create an instance of the ACE editor until the dynamically created script has
loaded.

Add a guard in the content setter to prevent calling methods on a JS proxy that might not
be up yet.

Huge thanks to @santiaago for pairing on this.
Use future to signal ACE is ready

Replace polling mechanism from the original impementation. Get test passing
again.
First pass at the preview layer
Remove some old code
Re-org to include JS, CSS, HTML and fonts in the package
Clean up some CSS
Enable theme and JS mode
Drop the incosolata font

It breaks cursor positioning in ACE
remove preview callback