Calculate discount price from user inputs.
Display a chart based on calculations by swiping right.
Next, Previous and “00” buttons on keyboard toolbar.
Formats textfields as currency.
Has a currency view (swipe left to right).
User can choose a home and a foreign currency from pickerviews.
Shows discount price in home and foreign currency.
Gets exchange rate async via YQL.
Saves exchange rate to file system, and reads if file exist.
Only gets rate from YQL if defined time has passed.
Uses USD if no other currency is picked.
