Change how unit tests are set up and run

Moves init.test.el to core/test/init.el and initializes the test
environment from within the current session, rather than through a bash
script middle man.

TODO: don't buffer the unit test results

core/test/helpers.el

@@ -0,0 +1,9 @@
+;; -*- no-byte-compile: t; -*-
+;;; core/test/helpers.el
+
+(defmacro insert!! (&rest text)
+  "Insert TEXT in buffer, then move cursor to last {0} marker."
+  `(progn
+     (insert ,@text)
+     (when (search-backward "{0}" nil t)
+       (replace-match "" t t))))