Update README.md

README.md

@@ -5,7 +5,7 @@ A port of the browser's `btoa` function.
 
 Uses `Buffer` to emulate the exact functionality of the browser's btoa (except that it supports unicode and the browser may not).
 
-It turns **b**inary data **to** base64-encoded **a**scii.
+It turns **b**inary data __to__ base64-encoded **a**scii.
 
     (function () {
       "use strict";