Include a Python fibonacci implementation in the perf folder

performance/python_fibonacci.py

@@ -0,0 +1,18 @@
+"""A naive Python implementation of the Fibonacci function, timed from start to end."""
+
+import time
+
+def fib(n):
+    if n <= 2:
+        return 1
+    else:
+        return fib(n - 1) + fib(n - 2)
+
+def main():
+    start_time = time.time()
+    print(fib(20))
+    end_time = time.time()
+    print('Test runtime: %f' % (end_time - start_time))
+
+if __name__ == '__main__':
+    main()