Alternative tagging strategies are not supported

[andrewmatthews]

We are using DataDog, which supports tagging StatsD metrics also. However the tagging strategy is different: <node_name>|<value>|<tag_name=tag_value>|<tag_name=tag_value>|....

It would be great to be able to configure a tagging strategy to use, and not couple MessageEntity to that strategy.

For now, we are going to fork the repository to make it usable with DataDog, but we will try to create a PR to use the strategy pattern for this to make it extendible.