Add Raven/sentry support.

Raven is only used on *.dijkdata.nl. This way the development errors
don't propagate to sentry.
Add Raven/sentry support.

Raven is only used on *.dijkdata.nl. This way the development errors
don't propagate to sentry.
Merge remote-tracking branch 'origin/raven-sentry' into raven-sentry
Merge pull request #34 from ddsc/raven-sentry

Sentry support added to the webclient.