add cursor key bindings

doc/reference.md

@@ -2,10 +2,10 @@
 
 ## Keys
 
-    down              (default "j")
-    up                (default "k")
-    updir             (default "h")
-    open              (default "l")
+    up                (default "k" and "<up>")
+    down              (default "j" and "<down>")
+    updir             (default "h" and "<left>")
+    open              (default "l" and "<right>")
     quit              (default "q")
     bot               (default "G")
     top               (default "gg")

opts.go

@@ -29,10 +29,14 @@ func init() {
 
 	gOpts.keys = make(map[string]Expr)
 
-	gOpts.keys["j"] = &CallExpr{"down", nil}
 	gOpts.keys["k"] = &CallExpr{"up", nil}
+	gOpts.keys["<up>"] = &CallExpr{"up", nil}
+	gOpts.keys["j"] = &CallExpr{"down", nil}
+	gOpts.keys["<down>"] = &CallExpr{"down", nil}
 	gOpts.keys["h"] = &CallExpr{"updir", nil}
+	gOpts.keys["<left>"] = &CallExpr{"updir", nil}
 	gOpts.keys["l"] = &CallExpr{"open", nil}
+	gOpts.keys["<right>"] = &CallExpr{"open", nil}
 	gOpts.keys["q"] = &CallExpr{"quit", nil}
 	gOpts.keys["G"] = &CallExpr{"bot", nil}
 	gOpts.keys["gg"] = &CallExpr{"top", nil}

ui.go

@@ -360,6 +360,14 @@ func (ui *UI) getExpr() Expr {
 					acc = append(acc, '<', 'b', 's', '2', '>')
 				case termbox.KeyTab:
 					acc = append(acc, '<', 't', 'a', 'b', '>')
+				case termbox.KeyArrowUp:
+					acc = append(acc, '<', 'u', 'p', '>')
+				case termbox.KeyArrowDown:
+					acc = append(acc, '<', 'd', 'o', 'w', 'n', '>')
+				case termbox.KeyArrowLeft:
+					acc = append(acc, '<', 'l', 'e', 'f', 't', '>')
+				case termbox.KeyArrowRight:
+					acc = append(acc, '<', 'r', 'i', 'g', 'h', 't', '>')
 				case termbox.KeyCtrlL:
 					acc = append(acc, '<', 'c', '-', 'l', '>')
 				case termbox.KeyEsc: