add signify
update signify to 1.1
rename to signify-osx

I still think it's silly, but if it means the difference between having
it at all or not, then I suppose it doesn't really matter.
rename properly

untested commits while commuting are rarely correct, no matter how trivial
add (totally not comprehensive) test block

discussion was here: https://github.com/Homebrew/homebrew/pull/31196#discussion_r18197926
signify-osx: add 1.1 bottle.