cabal: run the demo programs as tests

--HG--
extra : histedit_source : 6ac959aee513a341f143c25f060d89657f06c0c7
cabal: include test modules in package

--HG--
extra : histedit_source : 3cb4e4a587ec4d83cbb0172bf071e5cbfa13ff62
cabal: script to create and test packages
cabal: document migration of demo programs to tests

--HG--
extra : histedit_source : 7b0d0b4f8d9e4602070016989211c0738e27a42a
cabal: bump versions to 0.2.1

--HG--
extra : histedit_source : 193f54cf7ab9d96612bff93613f1662b69a64e3e
tag 0.2.1