Fix place ordinal calculation (#1067)

* Fix scoreboard place ordinalization in Python 3
* Extract ordinalization code to `CTFd.utils.humanize.numbers.ordinalize`.

tests/utils/test_humanize.py

@@ -0,0 +1,19 @@
+from CTFd.utils.humanize.numbers import ordinalize
+
+
+def test_ordinalize():
+    tests = {
+        1: "1st",
+        2: "2nd",
+        3: "3rd",
+        4: "4th",
+        11: "11th",
+        12: "12th",
+        13: "13th",
+        101: "101st",
+        102: "102nd",
+        103: "103rd",
+        111: "111th",
+    }
+    for t, v in tests.items():
+        assert ordinalize(t) == v