Issue #178 - Add histogram of job durations to flow stats.
Issue #178 - Only display histogram on flow page summary.
Issue #178 - Fix issue where whether SLA is set is always false.
Issue #178 - Display message if no job provides any job stats.
Issue #178 - Display warnings found during flow stats analysis.
Merge pull request #179 from davidzchen/robust-flow-summary

Flow Summary improvements