Add pins database

Related to @lurch's comments on #148, this PR contains a database of
pins for each Pi revision, along with various other bits of miscellany
(I might've gotten a bit carried away here...).

Any corrections/extensions welcome!

gpiozero/pins/pigpiod.py

@@ -9,6 +9,7 @@ str = type('')
 import pigpio
 
 from . import Pin
+from .data import pi_info
 from ..exc import (
     PinInvalidFunction,
     PinSetInput,
@@ -93,7 +94,14 @@ class PiGPIOPin(Pin):
     GPIO_PULL_UP_NAMES = {v: k for (k, v) in GPIO_PULL_UPS.items()}
     GPIO_EDGES_NAMES = {v: k for (k, v) in GPIO_EDGES.items()}
 
+    PI_INFO = None
+
     def __new__(cls, number, host='localhost', port=8888):
+        # XXX What about remote pins? This should probably be instance
+        # specific rather than class specific for pigpio. Need to check how
+        # to query remote info though...
+        if cls.PI_INFO is None:
+            cls.PI_INFO = pi_info()
         try:
             return cls._PINS[(host, port, number)]
         except KeyError:
@@ -107,7 +115,7 @@ class PiGPIOPin(Pin):
             self._host = host
             self._port = port
             self._number = number
-            self._pull = 'up' if number in (2, 3) else 'floating'
+            self._pull = 'up' if cls.PI_INFO.pulled_up('GPIO%d' % number) else 'floating'
             self._pwm = False
             self._bounce = None
             self._when_changed = None
@@ -150,7 +158,7 @@ class PiGPIOPin(Pin):
             self.frequency = None
             self.when_changed = None
             self.function = 'input'
-            self.pull = 'up' if self.number in (2, 3) else 'floating'
+            self.pull = 'up' if self.PI_INFO.pulled_up('GPIO%d' % self.number) else 'floating'
 
     def _get_function(self):
         return self.GPIO_FUNCTION_NAMES[self._connection.get_mode(self._number)]
@@ -187,7 +195,7 @@ class PiGPIOPin(Pin):
     def _set_pull(self, value):
         if self.function != 'input':
             raise PinFixedPull('cannot set pull on non-input pin %r' % self)
-        if value != 'up' and self._number in (2, 3):
+        if value != 'up' and self.PI_INFO.pulled_up('GPIO%d' % self._number):
             raise PinFixedPull('%r has a physical pull-up resistor' % self)
         try:
             self._connection.set_pull_up_down(self._number, self.GPIO_PULL_UPS[value])