Fix unhandled exception for invalid numeric SteamIDs (#248)

Too big integers or numeric strings raise TypeError in make_steam64 instead of returning valid SteamID object with the invalid flag set.
Examples:
SteamID(111111111111111111111111111111111111111)
SteamID('11111111111111111111111111111111111111')

steam/steamid.py

@@ -256,6 +256,9 @@ def make_steam64(id=0, *args, **kwargs):
             # 64 bit
             elif value < 2**64:
                 return value
+            # invalid account id
+            else:
+                accountid = 0
 
         # textual input e.g. [g:1:4]
         else:

tests/test_steamid.py

@@ -121,6 +121,12 @@ class SteamID_initialization(unittest.TestCase):
         self.compare(SteamID("invalid_format"),
                      [0, EType.Invalid, EUniverse.Invalid, 0])
 
+    def test_arg_too_large_invalid(self):
+        self.compare(SteamID(111111111111111111111111111111111111111),
+                     [0, EType.Invalid, EUniverse.Invalid, 0])
+        self.compare(SteamID("1111111111111111111111111111111111111"),
+                     [0, EType.Invalid, EUniverse.Invalid, 0])
+
     ######################################################
     # KWARGS
     ######################################################