Create Handler on looper of given context, transparent activity

Two fixes:
- The masterHandler should be created on the looper of the given context not on the looper of the current thread. I had the Exception "Can't create handler inside thread that has not called Looper.prepare()" because MemorizingTrustManger was initialized from a background thread without a looper (AsyncTask).

- Make activity in example app transparent and remove warnings by adding min and target sdk