Add Server.mfa_level to query a server's 2FA requirement.

discord/server.py

@@ -86,12 +86,16 @@ class Server(Hashable):
         Indicates if the server is a 'large' server. A large server is defined as having
         more than ``large_threshold`` count members, which for this library is set to
         the maximum of 250.
+    mfa_level: int
+        Indicates the server's two factor authorisation level. If this value is 0 then
+        the server does not require 2FA for their administrative members. If the value is
+        1 then they do.
     """
 
     __slots__ = ['afk_timeout', 'afk_channel', '_members', '_channels', 'icon',
                  'name', 'id', 'owner', 'unavailable', 'name', 'region',
                  '_default_role', '_default_channel', 'roles', '_member_count',
-                 'large', 'owner_id' ]
+                 'large', 'owner_id', 'mfa_level' ]
 
     def __init__(self, **kwargs):
         self._channels = {}
@@ -180,6 +184,7 @@ class Server(Hashable):
         self.unavailable = guild.get('unavailable', False)
         self.id = guild['id']
         self.roles = [Role(server=self, **r) for r in guild.get('roles', [])]
+        self.mfa_level = guild.get('mfa_level')
 
         for mdata in guild.get('members', []):
             roles = [self.default_role]