Revert "fix gradle download URL"

This reverts commit e60274ab3397d0e9bac82e6ed1a58a1ad670da72.
gradle: update all things gradle for Android Studio compatibility

@tux-mind: the wrapper url you had set was throwing a handshake error in Android Studio, on my machine at least, so I reverted your commit.
Feel free to re-change this if the current url doesn't work for you.

To anyone who wants to build dSploit: make sure to update to the latest SDK, build-tools & build-repository in your SDK manager.