Package exceptions as separate entities and add in_app to stacktrace fra...

Great Library!

I re-wrote setException and getStackTrace to package each exception as its own entry instead of compressing all exceptions and related stack traces into one.

This allows the sentry server to differentiate exceptions and root causes and also separate the stack traces for each exception.

I also added the in_app flag to getStackTrace and set it to true if the package name on the frame didn't match one of a few known packages (android.*, java.*, com.android.*, and dalvik.*).  Its not a perfect filter but it does allow you to collapse stack traces when viewing them in the sentry server.