Add release date for new BCM2837-based Pi 2B

I think this is all that's needed to make pi_info accurate

Author: bennuttall

gpiozero/pins/data.py

@@ -848,7 +848,7 @@ def from_revision(cls, revision):
                     'A':    '2013Q1',
                     'B':    '2012Q1' if pcb_revision == '1.0' else '2012Q4',
                     'A+':   '2014Q4',
-                    'B+':   '2014Q3',
+                    'B+':   '2014Q3' if pcb_revision == '1.1' else '2016Q3',
                     '2B':   '2015Q1',
                     'CM':   '2014Q2',
                     '3B':   '2016Q1',