Enumerate habits in list subcommand.

src/habitmgr.rs

@@ -88,9 +88,9 @@ impl HabitMgr
 	pub fn list(&mut self, all:bool, verbose:bool)
 	{
 		self.import_habits();
-		for i in &self.habits
+		for (i, habit) in self.habits.iter().enumerate()
 		{
-			println!("{}", i.get_name());
+			println!("{}\t{}", i, habit.get_name());
 		}
 	}
 }