fix(locators): Improve custom locators message

Increase readability of custom locator message by displaying each argument instead of the arguments object.

lib/locators.js

@@ -65,7 +65,7 @@ ProtractorBy.prototype.addLocator = function(name, script) {
         return driver.findElements(
             webdriver.By.js.apply(webdriver.By, findElementArguments));
       },
-      message: 'by.' + name + '("' + locatorArguments + '")'
+      message: 'by.' + name + '("' + Array.prototype.join.call(locatorArguments, '", "') + '")'
     };
   };
 };