Fix Array Semigroup append: concatArray used table.concat (string join) instead of concatenating two arrays. Breaks Array <> and downstream (e.g. traverse over the Array applicative, foldable-traversable). Fixed element-wise. (#4 by @Renegatto)

Lua 5.1 FFI compatibility fixes (Bounded/Show Char & Int), foreign-comment link fix in EuclideanRing, and a fail-fast build script. See #5 and #6.