This removes the dependency on github.com/golang/protobuf, which does not accept
custom types anymore (since it has been reimplemented on top of the v2 api)

RavenLogger does not implement ZeroLogger, which is a problem for some clients,
especially xbus-http.

This helper add a Str() context to a logger

This function returns a new logger that will capture the logs of its parent.
It is meant to be called in subtests.

raven-go is deprecated, we have to support the new lib