Fix bugs in vector/_subvec

There were two independent bugs in `vector/_subvec` that were turned up by our `test.check` testing.

The first was that the order of the arguments was wrong and `stop-raw` and `start-raw` were flipped.

The second was that `stop` wasn't max'ed with 0, which meant it could sometimes be negative, leading to an `IndexOutOfBoundsException`.

src/propeller/push/instructions/vector.cljc

@@ -208,9 +208,9 @@
   ^{:stacks #{:integer}}
   (fn [stack state]
     (make-instruction state
-                      (fn [stop-raw start-raw vect]
+                      (fn [start-raw stop-raw vect]
                         (let [start (min (count vect) (max 0 start-raw))
-                              stop (min (count vect) (max start-raw stop-raw))]
+                              stop (min (count vect) (max 0 start-raw stop-raw))]
                           (subvec vect start stop)))
                       [:integer :integer stack]
                       stack)))