Added description for fractional images #9

* closes #9

README.mdown

@@ -15,7 +15,7 @@ If you'd like to instantiate it yourself with a custom number of stars use:
 	DLStarRatingControl *ratingControl = [[DLStarRatingControl alloc] initWithFrame:CGRectMake(0, 0, 320, 230) andStars:3 isFractional:YES];
 
 You can set a default value by setting `ratingControl.rating=2.5` and hook up a `DLStarRatingDelegate` to get notified when the user has
-changed the rating. 
+changed the rating. _Note: if you want to use fractional stars, you have to provide images with width [divisible by 10](https://github.com/dlinsin/DLStarRating/issues/9#issuecomment-4438728)._
 
 To customize the stars, simply replace `star.png`/`star@2x.png` and `star_highlighted.png`/`star_highlighted@2x.png` under images.