Initial Commit
WIP: Basic tip calculator as learning project for iOS

Implements v basic functionality.

-- Given a bill amount, computes tip and total.
-- Tip amounts configurable (and persistent) via settings view.
-- Can independently select tip percentage for each level of service.
-- Simplifying assumption. Default service level is "good". (Could also
   allow this to be configured, but probably overkill for a simple app.)
Merge branch 'master' of https://github.com/iconicadigital/tip_calculator