Auto-hide the text view’s scroll bars

This is for users who have set “show scroll bars” to “always” (or auto and am using a mouse).

Closes #527.

Frameworks/OakTextView/src/OakDocumentView.mm

@@ -92,6 +92,7 @@ private:
 		textScrollView = [[NSScrollView alloc] initWithFrame:NSZeroRect];
 		textScrollView.hasVerticalScroller   = YES;
 		textScrollView.hasHorizontalScroller = YES;
+		textScrollView.autohidesScrollers    = YES;
 		textScrollView.borderType            = NSNoBorder;
 		textScrollView.documentView          = textView;
 		[self addSubview:textScrollView];