Fix problem when http:// contains upper case

lib/index.js

@@ -14,7 +14,7 @@ var yellowLabTools = function(url, options) {
 
     } else {
 
-        if (url.indexOf('http://') !== 0 && url.indexOf('https://') !== 0) {
+        if (url.toLowerCase().indexOf('http://') !== 0 && url.toLowerCase().indexOf('https://') !== 0) {
             url = 'http://' + url;
         }