CurieEEPROM refactor

This PR refactors CurieEEPROM library, syncing it with AVR version.
Since EEPROM on Curie chip is based on OTP flash storage, the minimum write
size is 4 bytes. The current implementation brings some problems like
http://forum.arduino.cc/index.php?topic=421348.0 , and the examples are
quite broken.

The refactor also changes the name, from CurieEEPROM to EEPROM, so code for
AVR sketches compiles out of the box. The new library resolution engine
(from IDE 1.6.8 onward) handles this perfectly but we can stick to older name
if we need compatibility with older IDEs.

Author: facchinm