Modify storymap scripts to allow issue rendering.

The following data structure is passed to map.handlebars to be
rendered:

{ unassigned: [<StoryData>, ...],
  assigned: { <epicName>: { <sprintName>: [<StoryData>, ...],
                            ...
                          },
	      ...
	    }
}

where <StoryData> is defined as follows:

{ name: <name>,
  number: <number>,
  assignee: <assignee>,
  state: <state>,
  comments: <comments>,
  cost: <cost>,
  priority: <priority>
}