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.

Closes https://github.com/psycholold/SensorReader/issues/13, https://github.com/psycholold/SensorReader/issues/15 and https://github.com/psycholold/SensorReader/issues/16
Merge pull request #19 from psycholold/13-fix-timestamp

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