{{alias}}( fcns, clbk[, thisArg] )
    Executes functions in series, passing the results of one function as
    arguments to the next function.

    The last argument applied to each waterfall function is a callback. The
    callback should be invoked upon a series function completion. The first
    argument is reserved as an error argument (which can be `null`). Any results
    which should be passed to the next function in the series should be provided
    beginning with the second argument.

    If any function calls the provided callback with a truthy `error` argument,
    the waterfall suspends execution and immediately calls the completion
    callback for subsequent error handling.

    Execution is *not* guaranteed to be asynchronous. To ensure asynchrony, wrap
    the completion callback in a function which either executes at the end of
    the current stack (e.g., `nextTick`) or during a subsequent turn of the
    event loop (e.g., `setImmediate`, `setTimeout`).

    Parameters
    ----------
    fcns: Array<Function>
        Array of functions.

    clbk: Function
        Callback to invoke upon completion.

    thisArg: any (optional)
        Function context.

    Examples
    --------
    > function foo( next ) { next( null, 'beep' ); };
    > function bar( str, next ) { console.log( str ); next(); };
    > function done( error ) { if ( error ) { throw error; } };
    > var fcns = [ foo, bar ];
    > {{alias}}( fcns, done );


{{alias}}.factory( fcns, clbk[, thisArg] )
    Returns a reusable waterfall function.

    Parameters
    ----------
    fcns: Array<Function>
        Array of functions.

    clbk: Function
        Callback to invoke upon completion.

    thisArg: any (optional)
        Function context.

    Returns
    -------
    fcn: Function
        Waterfall function.

    Examples
    --------
    > function foo( next ) { next( null, 'beep' ); };
    > function bar( str, next ) { console.log( str ); next(); };
    > function done( error ) { if ( error ) { throw error; } };
    > var fcns = [ foo, bar ];
    > var waterfall = {{alias}}.factory( fcns, done );
    > waterfall();
    > waterfall();
    > waterfall();

    See Also
    --------