Make value getters/setters more consistent

See #6

calendar.go

@@ -16,7 +16,7 @@ type Calendar struct {
 	monthLabel *Label
 	
 	on struct {
-		edit event.FuncBroadcaster
+		valueChange event.FuncBroadcaster
 	}
 }
 
@@ -33,13 +33,13 @@ func NewCalendar (tm time.Time) *Calendar {
 	prevButton.SetIcon(tomo.IconGoPrevious)
 	prevButton.OnClick(func () {
 		calendar.prevMonth()
-		calendar.on.edit.Broadcast()
+		calendar.on.valueChange.Broadcast()
 	})
 	nextButton := NewButton("")
 	nextButton.SetIcon(tomo.IconGoNext)
 	nextButton.OnClick(func () {
 		calendar.nextMonth()
-		calendar.on.edit.Broadcast()
+		calendar.on.valueChange.Broadcast()
 	})
 	calendar.monthLabel = NewLabel("")
 	calendar.monthLabel.SetAlign(tomo.AlignMiddle, tomo.AlignMiddle)
@@ -60,17 +60,22 @@ func NewCalendar (tm time.Time) *Calendar {
 	return calendar
 }
 
-// SetTime sets the date the calendar will display.
-func (this *Calendar) SetTime (tm time.Time) {
+// Value returns the time this calendar is displaying.
+func (this *Calendar) Value () time.Time {
+	return this.time
+}
+
+// SetValue sets the date the calendar will display.
+func (this *Calendar) SetValue (tm time.Time) {
 	if this.time == tm { return }
 	this.time = tm
 	this.refresh()
 }
 
-// OnEdit sets a function to be called when the user changes the date on the
-// calendar.
-func (this *Calendar) OnEdit (callback func ()) {
-	this.on.edit.Connect(callback)
+// OnValueChange sets a function to be called when the user changes the date on
+// the calendar.
+func (this *Calendar) OnValueChange (callback func ()) {
+	this.on.valueChange.Connect(callback)
 }
 
 func (this *Calendar) prevMonth () {