fix typo

Author: etpinard

README.md

@@ -56,7 +56,7 @@ var plotlyCore = require('plotly.js/lib/core');
 
 // Load in the trace types for pie, and choropleth
 plotlyCore.register([
-    require('plotly.js/lib/pie');
+    require('plotly.js/lib/pie'),
     require('plotly.js/lib/choropleth');
 ]);