Add three Features (Relative font-size, label in donut, and number shortener)

* Relative font-size : permit to avoid summaryTitle or summaryNumber exceeds the donut.
* Label in the donut : like tip, but title is set in the summaryTitle <p />.
* Number shortener : e. g. to print 200K rather than 200000 (or 200M rather than 200000000).

Example for the first two features : http://jsfiddle.net/CDLXE/6/
Example for the last one : http://jsfiddle.net/CDLXE/7/