Support in_app field for stacktrace frames

wrap-sentry and stacktrace now take an optional namespaces arg which
should be a list of namespace prefixes which you want to be treated as
in_app by sentry.

The stacktrace map is changed to support the exception interface.

![screenshot 2014-10-16 10 23 58](https://cloud.githubusercontent.com/assets/78506/4660778/bf31afea-551b-11e4-93dd-471a02124310.png)

![screenshot 2014-10-16 10 24 14](https://cloud.githubusercontent.com/assets/78506/4660794/dbe89b1c-551b-11e4-93d0-d75a513ad483.png)