Add support for Discord's slow mode.

Adds the following:

* `slowmode_delay` for `TextChannel.edit`
* `slowmode_delay` attribute for `TextChannel`

3 files changed, 24 insertions, 8 deletions

diff --git a/discord/abc.py b/discord/abc.py
index 365fcebf..0ca11452 100644
--- a/discord/abc.py
+++ b/discord/abc.py
@@ -231,6 +231,11 @@ class GuildChannel:
         else:
             parent_id = parent and parent.id
 
+        try:
+            options['rate_limit_per_user'] = options.pop('slowmode_delay')
+        except KeyError:
+            pass
+
         lock_permissions = options.pop('sync_permissions', False)
 
         try:
diff --git a/discord/channel.py b/discord/channel.py
index eb157ad9..32faf983 100644
--- a/discord/channel.py
+++ b/discord/channel.py
@@ -78,10 +78,15 @@ class TextChannel(discord.abc.Messageable, discord.abc.GuildChannel, Hashable):
     position: :class:`int`
         The position in the channel list. This is a number that starts at 0. e.g. the
         top channel is position 0.
+    slowmode_delay: :class:`int`
+        The number of seconds a member must wait between sending messages
+        in this channel. A value of `0` denotes that it is disabled.
+        Bots and users with :attr:`~Permissions.manage_channels` or
+        :attr:`~Permissions.manage_messages` bypass slowmode.
     """
 
     __slots__ = ('name', 'id', 'guild', 'topic', '_state', 'nsfw',
-                 'category_id', 'position', '_overwrites')
+                 'category_id', 'position', 'slowmode_delay', '_overwrites')
 
     def __init__(self, *, state, guild, data):
         self._state = state
@@ -98,6 +103,8 @@ class TextChannel(discord.abc.Messageable, discord.abc.GuildChannel, Hashable):
         self.topic = data.get('topic')
         self.position = data['position']
         self.nsfw = data.get('nsfw', False)
+        # Does this need coercion into `int`? No idea yet.
+        self.slowmode_delay = data.get('rate_limit_per_user', 0)
         self._fill_overwrites(data)
 
     async def _get_channel(self):
@@ -133,21 +140,24 @@ class TextChannel(discord.abc.Messageable, discord.abc.GuildChannel, Hashable):
 
         Parameters
         ----------
-        name: str
+        name: :class:`str`
             The new channel name.
-        topic: str
+        topic: :class:`str`
             The new channel's topic.
-        position: int
+        position: :class:`int`
             The new channel's position.
-        nsfw: bool
+        nsfw: :class:`bool`
             To mark the channel as NSFW or not.
-        sync_permissions: bool
+        sync_permissions: :class:`bool`
             Whether to sync permissions with the channel's new or pre-existing
             category. Defaults to ``False``.
         category: Optional[:class:`CategoryChannel`]
             The new category for this channel. Can be ``None`` to remove the
             category.
-        reason: Optional[str]
+        slowmode_delay: :class:`int`
+            Specifies the slowmode rate limit for user in this channel. A value of
+            `0` disables slowmode. The maximum value possible is `120`.
+        reason: Optional[:class:`str`]
             The reason for editing this channel. Shows up on the audit log.
 
         Raises
diff --git a/discord/http.py b/discord/http.py
index 2d5c67fb..6c2b548c 100644
--- a/discord/http.py
+++ b/discord/http.py
@@ -495,7 +495,8 @@ class HTTPClient:
 
     def edit_channel(self, channel_id, *, reason=None, **options):
         r = Route('PATCH', '/channels/{channel_id}', channel_id=channel_id)
-        valid_keys = ('name', 'parent_id', 'topic', 'bitrate', 'nsfw', 'user_limit', 'position', 'permission_overwrites')
+        valid_keys = ('name', 'parent_id', 'topic', 'bitrate', 'nsfw',
+                      'user_limit', 'position', 'permission_overwrites', 'rate_limit_per_user')
         payload = {
             k: v for k, v in options.items() if k in valid_keys
         }