Removed jQuery dependency

JQuery doesn't add any value in this binding. This makes it possible to
use the binding without jQuery.
Destroy ace editor instance when element is removed

This will prevent an ever growing instances list and possible memory
leaks.
Remove unused variable
Added read only option
Merge pull request #2 from informaat-ipe/read-only-option

Added read only option
Merge pull request #1 from informaat-ipe/refactoring-and-destruction

Removed jQuery dependency and added disposal callback