Pass instance to parent callback, fixes #22, fixes #100

[tsrahm]

By passing the instance of the EmailEditor to the parent in the loadEditor function, the parent has access to the instance when the parent's onLoad function is fired.

[tsrahm]

I don't like the idea of using setInterval to delay the invocation of the loadDesign method. By passing the editor instance to the callback, it is available immediately.

[OlivierJM]

Thanks for the explanation