Backtrace app recognition issues

[rabidpraxis]

We had a user whose notice was marking dependency backtrace lines as application backtraces. The Honeybadger web interface was attempting to build links to GitHub for his project, and it was obviously not working.

It would be good to double-check that any elixir updates have not introduced any regressions in this area, or perhaps expand test coverage to make sure the app is being recognized correctly.