Add "rollbar.person_data" to rollbar scope

[ransombriggs]

I was attempting to add the logged in user to my rollbar reports and setting the rack env data did not work. It did when I used the default reporter and tracked the difference down to here https://github.com/rollbar/rollbar-gem/blob/master/lib/rollbar/middleware/rack.rb#L33 . This just duplicates that functionality in the pliny reporter. The test is a little clunky in that it tests some rollbar functionality, but I wanted to make sure that the person data is picked up correctly.

[ransombriggs]

@mikehale extracted the logic from our app, does this look good?

[mikehale]

👍

[gudmundur]

LGTM