[#465] Sanitize header name on SlickGrid view

Change logic of sanitizing. Previously either original value
or content of element with matching selector was used as column
header.

After this change original value with applied encoding of
html entities will be used

src/view.slickgrid.js

@@ -161,13 +161,7 @@ my.SlickGrid = Backbone.View.extend({
     }
 
     function sanitizeFieldName(name) {
-      var sanitized;
-      try{
-        sanitized = $(name).text();
-      } catch(e){
-        sanitized = '';
-      }
-      return (name !== sanitized && sanitized !== '') ? sanitized : name;
+      return $('<div>').text(name).html();
     }
 
     _.each(this.model.fields.toJSON(),function(field){