Integration with new sentry SDK


#1

Hello, @bogdan, Thanks for dramatiq!

As described at Raven README.md Raven SDK is being phased out for Sentry-Python.

It will be cool to update docs(raven example) and add official integration to sdk.

https://getsentry.github.io/sentry-python

I created issue here: https://github.com/Bogdanp/dramatiq/issues/114