Clojurians Log v2

hi @msolli, thanks for writing proletarian, it is a great library. i made the following proposal https://github.com/msolli/proletarian/pull/13 to facilitate testing systems which use proletarian as a component. it turned out that there was one tiny missing piece to make this work. i hope that the description was speaking enough, but i am happy to write more about the intended use case.

any comments appreciated.