Adding support for ADXL335 accelerometer

Adding support for the ADXL335, which is the analog cousin of the ADXL345 (I2C) which @rwaldron is working on.  This thing is really just an analog accelerometer, so the controller is the same.  So I busted out the constants and made a copy.  Perhaps there is a more idiomatic way of doing this, but it was easy and it gets the job done.

Included is example, doc, and fritzing
Slick