Add coding exercises for Facebook interviews

Add attempts at solving coding problems to Briefcase.

scratch/facebook/cafe-order-checker.py

@@ -0,0 +1,19 @@
+def orders_are_sorted(take_out, dine_in, audit):
+    if len(take_out) + len(dine_in) != len(audit):
+        return False
+
+    i, j = 0, 0
+    for x in audit:
+        if i < len(take_out) and take_out[i] == x:
+            i += 1
+        elif j < len(dine_in) and dine_in[j] == x:
+            j += 1
+        else:
+            return False
+    return True
+
+
+assert orders_are_sorted([1,3,5], [2,4,6], [1,2,4,3,6,5])
+assert not orders_are_sorted([1,3,5], [2,4,6], [1,2,4,5,6,3])
+assert orders_are_sorted([], [2,4,6], [2,4,6])
+print("Success!")