Reference for xbee
Added I2Cdev libraires

Added examples fro MPU6050 and others with I2C jrowberg/i2cdevlib
Added more Arduino examples for SD & Xbee

Added the SD Datalogger libraries from sparkfun and Xbee/Xbee Pro
libraries fro arduino from Google Code
Pressure sensor files

Added arduino examples for the BMP180 pressure sensor