getCategoriesCommand.elm

-- getCategoriesCommand is responsible for making the HTTP GET
-- call to fetch the tags.  |> is a pipe operator and I'm using to create a 'pipeline'.  
-- The Json.Decode.list tagDecoder is passed to the Http.get call as the last parameter
-- and is responsible for turning the JSON Array of categories into an Elm list of Categories.
-- The List of Categories from the decoder become the parameter of the DataRecieved Msg and
-- eventually become the navigation list
getCategoriesCommand : Cmd Msg
getCategoriesCommand =
    Json.Decode.list categoryDecoder
        |> Http.get "http://localhost:8088/categories"
        |> Http.send DataReceived