Streams 138

basic push implementation w/ small fixes to jsonschema and serializer
see https://github.com/w2ogroup/streams-examples/tree/master/datasift-webhook
for an example of how to deploy this provider
Perhaps - it would be great if there were one ObjectMapper implementation that would be compatible with all existing and future modules and any datetime format anywhere on the web.  I'm all for trying to build one, but that goes beyond the scope of this story.  In any case I think it's appropriate for modules that require tweaks to StreamsJacksonMapper to extend it internally, rather than updating streams-pojo.  
However I'd like to see something in streams-pojo that could determine the appropriate Mapper for any document, even if the Mapper was in a contrib module, and perhaps run all serialization/deserialization operations through a utility class.