Changes from Discord API docs (#149)

* Remove undocumented OPCode

This is not documented in the Discord API docs, and is claimed not to usable by (or useful to) bots.

* Add missing ChannelType

disco/gateway/packets.py

@@ -15,4 +15,3 @@ class OPCode(object):
     INVALID_SESSION = 9
     HELLO = 10
     HEARTBEAT_ACK = 11
-    GUILD_SYNC = 12

disco/types/channel.py

@@ -20,6 +20,7 @@ class ChannelType(object):
     GROUP_DM = 3
     GUILD_CATEGORY = 4
     GUILD_NEWS = 5
+    GUILD_STORE = 6
 
 
 class PermissionOverwriteType(object):