list and Chain documentation

[timcdlucas]

Hi all,

A few issues I've found with the documentation.

Firstly, as far as I can see there's no easy way to get documentation for list. ?list would be very useful.

Secondly, ?Chain says "Model and output modules may not be chained." But output modules can be chained and is in fact the only way to do something like

work2 <- workflow(UKAnophelesPlumbeus,
                 UKAir,
                 OneHundredBackground,   
                 list(RandomForest, LogisticRegression),
                 Chain(PrintOccurrenceMap, PrintMap))

I will try to get round to fixing this later point myself. Not exactly sure the best approach for the previous former point.

[timcdlucas]

This is partially the same issue as #32.