Fix typo in comment

lib/screenshotHandler.js

@@ -94,9 +94,9 @@ var screenshotHandler = function() {
         return deferred.promise;        
     };
 
-    // If the page doesn't set a background color, the default PhantomJS one is transparent.
+    // If the page doesn't set a bg color, the default PhantomJS one is transparent
     // When transforming PNG to JPG, transparent pixels become black.
-    // This is why we need to had a transparent background.
+    // This is why we need to add a transparent background.
     this.addWhiteBackground = function(image) {
         var deferred = Q.defer();