Rename common-lisp directory to lisp

I could have renamed common-lisp to common_lisp. I think Nix prefers underscores
to hyphens.

lisp/default.nix

@@ -0,0 +1,16 @@
+{ depot ? import <depot> {},
+  universe ? import <universe> {},
+  ...
+}:
+
+depot.nix.buildLisp.program {
+  name = "unit-testing";
+
+  deps = with universe.third_party.lisp; [
+    prove
+  ];
+
+  srcs = [
+    ./unit-testing.lisp
+  ];
+}

lisp/main.lisp

@@ -0,0 +1,15 @@
+(in-package #:cl-user)
+(defpackage #:utils
+  (:documentation "Some utility functions and macros to wet my beak.")
+  (:use #:cl)
+  (:shadow #:type))
+(in-package #:utils)
+
+(defmacro type (name in out)
+  `(declaim (ftype (function ,in ,out) ,name)))
+
+(defmacro comment (&rest _forms) nil)
+
+(type add (int int) int)
+(defun add (a b)
+  (+ a b))

lisp/unit-testing.lisp

@@ -0,0 +1,13 @@
+(in-package #:cl-user)
+(defpackage #:my-test
+  (:documentation "Unit testing in Common Lisp.")
+  (:use #:cl))
+(in-package #:my-test)
+
+(plan 3)
+
+(ok (not (find 4 '(1 2 3))))
+(is 4 4)
+(isnt 1 #\1)
+
+(finalize)