elm-css-with-context

Simple port of arowM/elm-html-with-context to make it work with rtfeldman/elm-css.

This package is identical to arowM's, with a few small differences:

• I rewrote all of the functions myself, line by line, in a style that is a little easier for me to read (i.e., no left pizza or left-compose, slightly different argument names under the hood), mostly as a means of better understanding how the original package works.
• There's no WithContext.Lazy.lazy7, because Html.Styled.Lazy needs an argument to track styling info and WithContext.Lazy also needs to use an argument to track context info.
• I added a few extra comments here and there, to try to explain things as they became more clear to me.