Is there a recommended way of restricting input length?

First off, thanks for creating such a simple, useful plugin!

I find myself needing to limit the length of text a user may enter into the pell editor. I'm tempted to tack on an event listener and call `preventDefault` on the event object if the length of the pell editor's value is longer than N. Though, that seems like a kludge and like I'm working against the editor.

So, is there a recommended way of limiting the amount of text a user may enter into the pell editor? I'm looking at the source now and don't see any obvious solutions. Perhaps the event object could be passed to `settings.onChange` from within [`content.oninput`](https://github.com/jaredreich/pell/blob/master/src/pell.js#L123-L126)?

Start by reading src/pell.js around content.oninput at lines 123-126 and review how settings.onChange currently receives changes. Determine the intended behavior for limiting input length, including how pasted or edited content is handled, then verify the behavior with the existing test setup if applicable.

Written by the indexing model from the issue text.