Calculate extra time in minutes (trello 55)

  * adding new helper for converting seconds to minutes for views
  * removing formatting chore from Business model
  * each Option will only return its extra duration in seconds
Merge branch 'master' into db_duration
Renaming Errand property from additional_duration to delta_duration

* consistent with concept being used: a calculation
* all specs pass
Merge branch 'master' into db_duration

Conflicts:
	app/helpers/application_helper.rb
Changing added_duration to delta_duration
Merge pull request #31 from LightningLord/db_duration

Db duration