Refresh uses current contents if changed

Checks if microfiche contains a .microfiche-screen element, and if not assumes content has changed.

Yet another possibility would be to actually pass the new html string as an argument to Refresh, but this seems messy at first impression.

Or we could implement this sort of auto-checking somewhere else, in a way that allows `$('#thing').microfiche();` to be called on an element more than once, and have it reinitialize if changed. That could be the most intuitive, as it may not even require updating the docs.