Do not include STDERR in captured output

Closes #229

metric_fu was concatenating STDERR from flay to the captured
STDOUT, causing unexpected formatting of the flay report,
which causes parsing failures
Safely strip spaces from flay reported problems
Move flay result calculation out of to_h
Merge pull request #230 from metricfu/fix_captured_output

[Fix] Fix captured output to not append STDERR, fixes #229