Document failWithError parameter in authenticate()

[hsource]

Helps with #458. I don't know where to submit a change that would update http://www.passportjs.org/docs/authenticate/ but I'd be happy to help with that too

Checklist

• I have read the CONTRIBUTING guidelines.
• I have added test cases which verify the correct operation of this feature or patch.
• I have added documentation pertaining to this feature or patch.
• The automated test suite ($ make test) executes successfully.
• The automated code linting ($ make lint) executes successfully.

[coveralls]

Coverage remained the same at 98.87% when pulling 19cc7c2 on hsource:patch-1 into 882d65e on jaredhanson:master.

[coveralls]

Coverage remained the same at 98.87% when pulling 19cc7c2 on hsource:patch-1 into 882d65e on jaredhanson:master.

[KerimG]

What's the status on this?

[hsource]

This is purely a documentation change so should be submittable.

[rap2hpoutre]

I guess it could be merged!