Have keyboard widget manage its own help

Define help with keys
This means that keys and help are automatically in sync
This means that you can't define keys, but forget help
This unfortunately also means that formatting may not be quite as good

modules/victorops/widget.go

@@ -7,15 +7,6 @@ import (
 	"github.com/wtfutil/wtf/wtf"
 )
 
-// HelpText to display to users
-const HelpText = `
-	Keyboard commands for VictorOps
-
-	/: Show/hide this help window
-	arrow down: Scroll down the list
-	arrow up: Scroll up the list
-`
-
 // Widget contains text info
 type Widget struct {
 	wtf.TextWidget