Update readme

README.md

@@ -16,4 +16,5 @@ TODO:
 * ~~Add legend to image, based on the `symbols` dictionary.~~
 * Correspond hex colors to floss colors, where possible.
 * ~~(Maybe) add stitch count for each color.~~
-* (Maybe) add GUI.
+* ~~(Maybe) add GUI.~~
+* Make sure legend width doesn't exceed image width.