Fix regular expression (#172)

README.md

@@ -84,7 +84,7 @@ In addition to customizing behaviors for a specific element, you can also custom
 
 ```javascript
 app.config(['uiMask.ConfigProvider', function(uiMaskConfigProvider) {
-  uiMaskConfigProvider.maskDefinitions({'A': /[a-z], '*': /[a-zA-Z0-9]/});
+  uiMaskConfigProvider.maskDefinitions({'A': /[a-z]/, '*': /[a-zA-Z0-9]/});
   uiMaskConfigProvider.clearOnBlur(false);
   uiMaskConfigProvider.eventsToHandle(['input', 'keyup', 'click']);
 }