Run tests with Emacs' compile function

[bschmeck]

By using Emacs' native compile function, we can take advantage of the built-in features of compilation mode for free. That lets us do things like move between failures, open the relevant file and line from the stacktrace automatically and re-run the tests with a single keystroke. I was surprised at how little was required to get it all hooked up, honestly.

There's a little more work to be done: I haven't tried to integrate the "test after save" hook, and the face used by the stacktrace right now is ugly. But, this change does what I need it to and I wanted to see if there was any interest in merging something like this before I devoted time to features I don't personally use. I'm happy to keep running a forked version if you want to keep the current implementation of test reports.

This change was inspired by rspec-mode

[bschmeck]

I'll also work on cleaning up those test failures if there's interest in this PR.

[tonini]

@bschmeck I really like your idea. 👍 Could you try to fix the tests and I'll try to have a look at it by myself a soon as possible.

[dgutov]

Does it color the stack traces as well? I see alchemist-test--stacktrace-files-regex being removed here, but the standard Compilation mode regexps don't work well for me either.