rename tests file to main.lisp.

This was not needed in the end. I was having trouble with SLIME and I
was getting desperate at one point and starting changing
everything. It turns out I just needed to restart SLIME. At the time
of writing, I didn't know this or how to do that so I only noticed
when I restarted Emacs. It looks like stuff got messed-up in the cache
and SLIME couldn't find files/packages because it was looking for old
one which were either renames or deleted (due to me frantically
changing things).

tests/ritherdon-rest-tests.lisp

@@ -1,35 +0,0 @@
-;;;; ritherdon-rest-tests.lisp
-
-(in-package #:ritherdon-rest-tests)
-
-(def-suite all-tests
-  :description "The master suite of all ritherdon-rest tests.")
-
-(in-suite all-tests)
-
-;; These two examples show the 'full' call to the fiveAm test
-;; functions. This is just for reference. The 'namespace' is already
-;; 'imported' in 'package.lisp'.
-
-;; (fiveam:test sum-1
-;;   (fiveam:is (= 3 (+ 1 2))))
-
-;; (fiveam:run!)
-
-;; How you would normally create the tests -- with fiveAM already
-;; set-up in 'package.lisp' and not needing to be explicit about it
-;; here. This is similar to 'using static' in C#.
-
-(defun test-quasi()
-  (run! 'all-tests))
-
-(test dummy-tests
-  "Just a placeholder."
-  (is (listp (list 1 2)))
-  (is (= 5 (+ 2 3)))
-  (is (< 4 (+ 100 400))))
-
-(test dummy-tests-two
-  "This is another placeholder test.
-This is just to make sure everything is set-up properly."
-  (is (equal 4 4)))