Added COMBO mode to IMU test program. COMBO mode records data for 1 second then plays it back. Also, fetching data from the accelerometer FIFO seems to be working. I'm not sure what the cause of the problem was; perhaps it's related to the lockup issue.
Added write_byte_i2c().
Added read_byte_i2c().
Fixed mistake in *_byte_i2c() functions.
Changed init_imu() to use write_byte_i2c().