Add Circle CI
Add Circle CI

Elm has no way of explicitly compiling dependencies, and Circle needs
the dependencies to have been compiled in the `dependencies` step to be
able to cache them, so we run `elm make` in `dependencies => override`
and simply `echo "Success"` in the `test` phase.

ohanhi/elm-native-ui,craigambrose/elm-native-ui,elm-native-ui/elm-native-ui