Support all available annotation types for binary annotations

[kaisen]

According to the zipkin thrift spec, binary annotations can be of types bool, bytes, int, double, and string. py_zipkin currently only supports string binary annotations.

[codefromthecrypt]

I'd prefer if you don't implement this. It isn't likely the other types will carry forward, and zipkin really only supports string. openzipkin/zipkin#1499

[kaisen]

Thanks @adriancole, good to know!