Add description to README.md
Imp. add first prototype board and sketch

This prototype just capture value of 3-axis accelero-meter.

3-axis accelero-meter:
ADXL335
https://www.sparkfun.com/products/9269

Spark Core:
https://www.spark.io/

Fritzing for the Spark Core:
https://github.com/technobly/SparkCore-Fritzing