Have made a simpler structure for MCP3008/3004 and MCP3208/3204.

The code is running on my Pi and seems to be stable
 Have added MCP3301/3302/3304
 have implemented the "M" bit to allow Differential mode
 Have added an "absVal" for absolute values
 Have added a "relVal" for relative val from 0 to 1 (same as "value")
 left "value" for backwards compatabilety, but propse to delete it
 shifted Rx bits for MCP330x

 On branch master
 Your branch is up-to-date with 'origin/master'.

 Changes to be committed:
	modified:   gpiozero/__init__.py
	modified:   gpiozero/input_devices.py

 Untracked files:
	ZeroCombo11.py

 Date:      Mon Jan 18 20:25:36 2016 -0500

gpiozero/__init__.py

@@ -23,6 +23,11 @@ from .input_devices import (
     AnalogInputDevice,
     MCP3008,
     MCP3004,
+    MCP3208,
+    MCP3204,
+    MCP3301,
+    MCP3302,
+    MCP3304,
 )
 from .output_devices import (
     OutputDevice,