Allow jQuery options to accept 'update'

[blaknite]

This allows you to easily update textareas from a jQuery selector.

Useful if submitting via ajax and then clearing the content.

[domchristie]

This feature has been included in #68 (which also includes a fix for another issue). In the meantime, you may wish to do the following:

$('.my-selector`).data('expanding').update()