Consider replacing attribute lists with builder pattern

[jhbrown94]

myfunc attrs ...  =
...
 button ([Font.color blue] ++ attrs) {label = ..., onPress = ...}

seems uglier than something like

button |> Font.withColor blue |> attrs |> build {label = ..., onPress = ...}

With this change, one can compose attributes arguments with >>:

 ...
 myfunc (Font.color red >> Font.size large >> Font.underline) ...