fix(SensorReader): Correct timestamp in log and no output buffering

Fixes the timestamp in the output. Also removes buffering in the SensorReader for faster
updates.

Makes the following branches obsolete: https://github.com/psycholold/SensorReader/tree/13-timestamp and https://github.com/psycholold/SensorReader/tree/16-remove-buffering
Closes https://github.com/psycholold/SensorReader/issues/13 and https://github.com/psycholold/SensorReader/issues/16