Temperature and proper bit shifting

Hey Guys,

I've played a bit more with the mpu6050 driver and it turned out:

1) We were not converting the integers properly - the result from the sensor gives high and low bits for a 16bit signed integer, so the sign bit is 16th, not 32nd.

2) The sensor has a termometer - why not read it ;-) as a result I've renamed getMotion6 into getMotionAndTemp method

Now the reads are exactly the same as from plain-arduino program found here http://playground.arduino.cc/Main/MPU-6050?action=sourceblock&num=1

cc / @wojtekerbetowski @zuchos @viroos