Remove debug message
Merge remote-tracking branch 'origin/master' into alee/fix-267-evaluatejobmanager
Fix #267, reset bkEvaluateJobManager (clear evaluation queue) when
loading notebook.

Also make the evaluatejobmanager more robust by propagating errors
properly.
Merge pull request #489 from twosigma/alee/fix-267-evaluatejobmanager

Fix 267 evaluatejobmanager