Changes to make bounding box for selectable links more accurate.
Removed need for linkRanges.  Can now format a string containing clickable fields using DAAttributedStringFormatter's
formatString: method instead of formatString:linkRanges:, and DAAttributedLabel will automatically figure out where
the links are in the string.  Also, can just assign to text property of DAAttributedLabel, no need for the
setText:withLinkRanges: method.
Updated README:
	- instructions for adding additional fonts to DAFontSet.plist
	- no longer need to use linkRanges for clickable fields