Update task documentation

Updated the text to be more clear.  I'd like to see a pattern for implementing this as well.  I'm open to where this can be done.  The only example I have found is here: https://github.com/beego/beeweb/blob/master/models/models.go#L100

We should provide users with more clarity about good places to register and start tasks.  Revel has a standard mechanism and folder for organizing jobs, see the docs here: http://revel.github.io/manual/jobs.html
Merge pull request #117 from drewwells/patch-1

Update task documentation