mpr121 keypad

*_keypad.py defines one class KEYPAD for user programs. The class has 3 parameters i2c (the i2c bus to use), rq_pin (the requset pin) and address (the i2c device address, this will be 0x5a, 0x5b, 0x5c or 0x5d).
The KEYPAD object is made up of 2 types of object. 12 KEY objects which are accessed via the dictionary KEYPAD.key using the symbol on the keypad as the lookup symbol. And a PROXIMITY object (KEYPAD.keypad).
The PROXIMITY object has 2 user methods

Method	Type
.is_near()	boolean	is a finger near the keypad.
.was_near()	boolean	has anything been near the keypad since the .was_near() method was last executed.

`KEY` objects have 3 user methods

Method	Type
.is_pressed()	boolean	returns True if the key is being pressed.
.was_pressed()	boolean	returns True if the key has been pressed since the last call to the .was_pressed() method.
.get_presses()	integer	returns the number of times the key has been pressed since the last call to the .get_presses() method.

Object KEYPAD has no user methods, KEY states and PROXIMITY to the sensor are accessed by methods on the dictionay KEYPAD.key or object KEYPAD.keypad.