Demonstrate issue with exported types

[armanbilge]

Not for merging :)

This PR creates a test case with the compiler issue reported in #237 (reply in thread).

Then, it fixes it by replacing exported types with type aliases.

So, either this is a compiler bug, or exporting types doesn't do what we'd expect 😅

[erikerlandson]

Exporting types actually seems to be working very well. The problem is highly localized to two methods: show and showFull, and furthermore the problem is only occurring when the type is being mediated thru a type def, for example via type Temperature[V, U] = .... Note that mediating via Temperature (or EpochTime, etc) is not causing problems for any other methods, only these two.