Add form_note to lead form widget.

This is on all the other form widgets and I didn't notice. Most of
Madrona is actually using this. The structure changes slightly in this
version (it's not nested in the form), but it doesn't look like that
will affect styling. I hope. I'm not good at the CSS.
Merge pull request #262 from G5/form-notes

Add form_note to lead form widget.