Scroll top/bottom with Home and End keys

* Allows the use of the Home/End keys in order to scroll to the top or
   bottom of the list of stocks.

cmd/mop/main.go

@@ -114,6 +114,10 @@ loop:
 					} else if event.Key == termbox.KeyArrowDown || event.Ch == 'j' {
 						screen.IncreaseOffset(1, len(profile.Tickers))
 						redrawQuotesFlag = true
+					} else if event.Key == termbox.KeyHome {
+						screen.ScrollTop()
+					} else if event.Key == termbox.KeyEnd {
+						screen.ScrollBottom(len(profile.Tickers))
 					}
 				} else if lineEditor != nil {
 					if done := lineEditor.Handle(event); done {

screen.go

@@ -106,6 +106,19 @@ func (screen *Screen) DecreaseOffset(n int) {
 	}
 }
 
+func (screen *Screen) ScrollTop() {
+	screen.offset = 0
+}
+
+func (screen *Screen) ScrollBottom(max int) {
+	bottom := max - screen.height + screen.headerLine
+	if bottom > 0 {
+		screen.offset = bottom
+	} else {
+		screen.offset = 0
+	}
+}
+
 // Draw accepts variable number of arguments and knows how to display the
 // market data, stock quotes, current time, and an arbitrary string.
 func (screen *Screen) Draw(objects ...interface{}) *Screen {