Textarea can be too tall or short if textarea width changes

Resolves certain issues with textareas that are too tall or too short by adjusting the height when the width of the textarea changes.

I noticed that while a page is loading or under other circumstances where the layout changes, a textarea using `msd-elastic` may be improperly sized. In some cases this may be unavoidable, so it seemed important to watch the width of the textarea and adjust the height accordingly upon detecting a change.