Correct TOTP URI

Steam requires a 5-digit code, but most TOTP software has 6 digits
as the default when a length is not specified.

steam/guard.py

@@ -49,6 +49,7 @@ import json
 import subprocess
 import struct
 import requests
+import re
 from base64 import b64decode, b64encode
 from binascii import hexlify
 from time import time
@@ -179,6 +180,12 @@ class SteamAuthenticator(object):
         if resp['status'] != EResult.OK:
             raise SteamAuthenticatorError("Failed to add authenticator. Error: %s" % repr(EResult(resp['status'])))
 
+        try:
+            if not re.search('[&\?].*digits', resp['uri']):
+                resp['uri'] += '&digits=5'
+        except KeyError, AttributeError:
+            pass
+
         self.secrets = resp
         self.steam_time_offset = int(resp['server_time']) - time()