added readme to collections folder
added readme to collections folder

bryanedds/FSharpx.Extras,sideeffffect/FSharpx.Extras,fsprojects/FSharpx.Extras,bryanedds/FSharpx.Extras,bryanedds/FSharpx.Extras,fsprojects/FSharpx.Extras,sideeffffect/FSharpx.Extras