Limit urban to nsfw channels

cogs/links.py

@@ -154,6 +154,7 @@ class Links:
 
         EXAMPLE: !urban a normal phrase
         RESULT: Probably something lewd; this is urban dictionary we're talking about"""
+        if utils.channel_is_nsfw(ctx.message.channel, self.bot.db):
             await ctx.message.channel.trigger_typing()
 
             url = "http://api.urbandictionary.com/v0/define"
@@ -180,6 +181,8 @@ class Links:
                 await ctx.send('```\nError: Definition is too long for me to send```')
             except KeyError:
                 await ctx.send("Sorry but I failed to connect to urban dictionary!")
+        else:
+            await ctx.send("This command is limited to nsfw channels")
 
 
 def setup(bot):