Thanks for writing.
Upgrading your project to a higher API level should not break any libraries that are built against the previous API level. Additionally, the AppCompat library should also properly maintain compatibility.
Can you please try simply setting the target SDK of your project to be 22 and rebuilding it?
What you are getting is actually a warning and it should not prevent you from building and running your application.
Let me know if these hints don't work on your side and you need further assistance.