fix README

Author: lasconic

README.md

@@ -2,8 +2,8 @@ This is a plugin for MuseScore 1.2 to add harmonica tablature notation below the
 It currently supports the Hohner Highlander only, for both side (A highlander and D).
 If you want to have your harmonica added to the it, please contact me, or better, do a pull request.
 
-+ is for blow
-- is for draw
+- + is for blow
+- - is for draw
 
 For more info see