Suppress "undefined" messages in console where string errors are passed

Without this, "undefined" shows up in the console every time an error is passed via .error(String). This patch will attempt to display the err "object" as a fallback when the default behaviors fail.
Correct broken link to walkthrough video. Fixes #226
Fixing Cannot read property 'id' of undefined issue

This isn't a full fix as what it does is let kue bypass broken records.
Merge pull request #238 from roderickm/master

Correct broken link to walkthrough video. Fixes #226
Merge pull request #230 from michikono/patch-1

Suppress "undefined" messages in console where string errors are passed
Merge pull request #239 from michikono/patch-2

Fixing Cannot read property 'id' of undefined issue
Typo
Update Readme.md

Typo/grammar
Merge pull request #272 from kbsanders/patch-1

Typo
Merge pull request #273 from kbsanders/patch-2

Fix grammer in Readme.md
bump to 0.7.0
Unused variable: state
fix job.remove not to access singleton queue
fix job.remove not to access singleton queue
bump to 0.7.0
bump to 0.7.1
Job.toJSON() line wrapping for readability
improve error handling and fix swallowed processor exceptions
Pass worker context to processors so they can pause/resume workers.
improve error handling