Merge Provider and StatefulProvider (rrousselGit#35)

Idea: Throw error when Provider not found (rrousselGit#25)

Adds a Runtime Error letting the user know the Provider could not be
found, instead of silently failing.

new: Add Consumers with up to 6 parameters (rrousselGit#23)

* new: Add Consumers with up to 6 parameters

* format

Reintroduced StatefulProvider (rrousselGit#19)