add note about manual color hints behavior

README.md

@@ -3,7 +3,7 @@ Inline color hints for Sublime Text
 
 ![](https://raw.githubusercontent.com/braver/ColorHints/master/Colors.gif)
 
-Call up an inline color box displaying the color at the cursor(s). Live hints can be enabled always, never, or just in specific languages (via [scope selectors](https://www.sublimetext.com/docs/3/selectors.html)).
+Call up an inline color box displaying the color at the cursor(s). Live hints can be enabled always, never, or just in specific languages (via [scope selectors](https://www.sublimetext.com/docs/3/selectors.html)). The manually called hints will stick around until the file is edited.
 
 Currently the alpha (opacity) value is ignored because in these small samples, at low opacity, everything looks alike.