EXHIBIT 2

JOINT FILING AGREEMENT

The undersigned hereby agree to the joint filing of the Amendment No. 2 to the Schedule 13D to which this Agreement is attached.

Dated:  September 27, 2012

DISCOVERY GROUP I, LLC, for itself and as general partner of DISCOVERY EQUITY PARTNERS, L.P.
By:	Michael R. Murphy*
	Michael R. Murphy Managing Member
Daniel J. Donoghue*
Daniel J. Donoghue
Michael R. Murphy*
Michael R. Murphy
*By:	/s/ Mark Buckley
	Mark Buckley Attorney-in-Fact for Daniel J. Donoghue Attorney-in-Fact for Michael R. Murphy