New QR code linked to Peerunity donations

Old QR code was linked to a Bitcoin address. This new one is linked to
the address: PFWU1xDF1GaXFRUbC31gEXGHWyzAaweJcX which is the donation
address for Peerunity at: http://peer4commit.com/projects/74/donate
Merge pull request #135 from sandakersmann/master

New QR code linked to Peerunity donations.

Independently confirmed that the QR code matches the expected address for the Peerunity project on Peer4Commit. Merging the change.