Test for overlong manual scansions in known.py.

Related to #75.

src/test_known.py

@@ -0,0 +1,9 @@
+import unittest
+
+import known
+
+class TestKnown(unittest.TestCase):
+    def test_total_length(self):
+        for line, scansion in known.KNOWN_SCANSIONS.items():
+            length = sum(sum({"-": 0.5, "+": 1}[c] for c in shape) for word, shape in scansion)
+            self.assertLessEqual(length, 12, (line, scansion))