Tests

[kevans91]

I've got a branch queued up that basically rototills the libasignify API to take FILE * everywhere rather than opening files itself (mostly) -- mostly to support pkg or other applications that may want to just encrypt/decrypt/sign in memory (the new variants still take filenames). Before landing it, though, I'd like to at least put some frontend tests into place so we can have some confidence that asignify works like we're expecting before and after.

I've got some WIP[0] for this that currently just consists of some rogue shell scripts that speak TAP, but I'm not convinced that that's necessarily the best approach.

[0] master...kevans91:test