* If you load the squire.js script into a top-level page rather than an iframe,
it will add a Squire constructor to the global scope.
* The Squire constructor can be used to instantiate multiple instances on the
same page without having to load/parse/execute the full code every time.
* For each instance, create a new iframe, then call `new Squire( document )`,
with the document node for each iframe.
A willPaste event is now fired just before pasted content is inserted into the
document, allowing custom, arbitrary modification of the pasted content, or
prevention of the paste event altogether.
