Add coding exercises for Facebook interviews

Add attempts at solving coding problems to Briefcase.

scratch/facebook/permutation-palindrome.py

@@ -0,0 +1,17 @@
+from collections import Counter
+
+def is_palindrome(x):
+    return len([count for _, count in Counter(x).items() if count % 2 == 1]) <= 1
+
+
+xs = [("civic", True),
+      ("ivicc", True),
+      ("civil", False),
+      ("livci", False)]
+
+for x, expected in xs:
+    result = is_palindrome(x)
+    print(x)
+    print(result)
+    assert result == expected
+    print("Success!")