Bug Fix - due date, colorization

- Fixed bug that caused colorization to be way, way off.  Silly
  mistake.
- Fixed bug whereby due dates and durations were stored as-is, but
  should have been converted.
- On a related note, added Date::toEpochString,
  Duration::operator (std::string).

src/Duration.h

@@ -41,6 +41,7 @@ public:
 
   operator int ();
   operator time_t ();
+  operator std::string ();
 
   bool valid (const std::string&) const;
   void parse (const std::string&);