Alpha release 2

Jasper now supports variants (aka sum types), and matching on the constructor used to construct a variant value (aka case expressions, though we call them match expressions). This allows the creation of interesting data structures.

Other than that, there have been a few robustness improvements, and bugfixes.

Alpha release 1

Jasper is still unstable and under heavy development, but it has most of the expected functionality, and can be used to write short programs.