fix: replaces \u00A0 with  

Closes #521

src/converter.js

@@ -287,8 +287,8 @@ showdown.Converter = function (converterOptions) {
     text = text.replace(/\r\n/g, '\n'); // DOS to Unix
     text = text.replace(/\r/g, '\n'); // Mac to Unix
 
-    // Stardardize line spaces (nbsp causes trouble in older browsers and some regex flavors)
-    text = text.replace(/\u00A0/g, ' ');
+    // Stardardize line spaces
+    text = text.replace(/\u00A0/g, ' ');
 
     if (options.smartIndentationFix) {
       text = rTrimInputText(text);