Fixes #278, removing space in sensors label
Capture and log stderr output from called scripts

commands code would intermix stdout and stderr, which was bad.  First
subprocess code would just flat out ignore stderr which was also bad.
This captures it and logs it, which is good.
Merge pull request #279 from bdelbosc/master

Fixing #278 LMSensorsCollector fails to report sensors with invalid label
Merge pull request #280 from j2sol/master

Capture and log stderr output from called scripts
Remove a unneeded import
PEP8