Add directive to isolate scope for purchase inputs.

This commit adds a directive element to abstract the 'add purchase'
functionality for each atm withdrawal.  This enables scope isolation
from the parent controller.  Meaning that when an amount is input for a
new purchase for a particulary atm withdrawal, that same amount is not
broadcast to the rest of the atm withdrawals--it's isolated to only that
withdrawal.  Also made a few minor refactoring edits and set up some
scaffolding for the next iteration.
Project structure re-organization for modularity.
Add a 3rd atm withdrawal to data.json
Moved data/ to public/data/
Project structure refactor.

Refactored the project file structure to more closely align with the
yeoman file/project structure.  Also edited data.json file to include
double quotes on all name values.
Move dummy data set to external json file.

This commit moves the dummy data to an external json file.  To read in
the file, needed to add $http service and sort out promises.  Still need
to work through the directive to determine the best way to add a
purchase to a particulary ATM withdrawal.