Implement first part of reading BMP chip id
Make separate functions for sending START, STOP conditions
Implement twiRead() and read back BMP chip id in initBMP180()
Read out and save internal calibration data in initBMP180()
General cleanup of BMP code and first working version with
temperature readout
Do single block read and swap of BMP calibration data
Avoid sequence point ambiguity flagged by -Wall
Implement pressure reading with two TWI reads (should be possible with
a single 3-byte read)
Implement pressure reading with single TWI read and streamline
calibration calculations