Support for a Microchip 24xx32A EEPROM module attached to the I2C bus, like the DigiX has

Hi there!

I would very much like to use Bitlash on my [DigiX](http://www.kickstarter.com/projects/digistump/digix-the-ultimate-arduino-compatible-board-with-w) so I added some basic EEPROM support for it. The DigiX comes with a Microchip 24LC32AT-I EEPROM module onboard, attached to the I2C bus on address 0x50. This is a nice addition since the AT91SAM3X8E doesn't come with this functionality.

Since I'm fairly new to writing Arduino libraries, I'm sure some things can be done in a better way. The most obvious thing is that EEPROM access is actually quite slow. This is due to the I2C bus but also because I went for a simple implementation of eeread() and eewrite(). Doing reads/writes in blocks instead of individually and/or keeping a copy in RAM would probably help.

Anyway, I'm awaiting your feadback and I hope we can get this change merged in master eventually ;-)

cheers,
Remco