Actually import requests when doing from pwn import *

As per documentation, we claim to be importing `requests` globally
(https://github.com/Gallopsled/pwntools/blame/dev/docs/source/globals.rst#L100)

We should actually do this :)

pwn/toplevel.py

@@ -5,6 +5,7 @@
 import operator
 import os
 import re
+import requests
 import socks
 import signal
 import string