See also: [Code docs](http://andrewdavidmackenzie.github.io/flow/code/doc/flow_impl/index.html)
This crate defines a trait that implementations of flow 'functions' must implement in order for them to be invoked
by the flowrlib (or other) run-time library.
An example of a function implementing the `Implementation` trait can be found in the
docs for [`Implementation`](http://andrewdavidmackenzie.github.io/flow/code/doc/flow_impl/trait.Implementation.html)