After a lot of research, I got to a conclusion that uninstalls can't be tracked as "Package Removed" action is not broadcasted to all the apps except the one getting uninstalled.
And then I found a way of tracking uninstalls. I saved all uninstall user information by Sending a GCM and getting "Not Registered" error in the response(GCM gives "Not Registered" error for devices with the app uninstalled).
So now, when I installed Opera Max app and uninstalled it, it opened a webpage asking for "Uninstall Survey". How could they have done that?