Create MinutesTime

Concrete time class using minutes.  To switch to hours, simply copy and paste, update concreteToBase() and baseToConcrete(). Easy peasy.  No reason to implement costs, time and effort in anything other than doubles.  Concrete money class could implement toString() so they output the symbol for the currency type like '$'
Merge pull request #3 from phewitt2/patch-3

Create MinutesTime