Fix API reference.

Added the required Group ID (gid) for /groups/{gid}/chat for the API reference documentation

src/routes/apiv2.coffee

@@ -455,6 +455,7 @@ module.exports = (swagger, v2) ->
       spec:
         path: "/groups/{gid}/chat"
         description: "Get all chat messages"
+        parameters: [path('gid','Group to return the chat from ','string')]
       middleware: [auth.auth, groups.attachGroup]
       action: groups.getChat
 
@@ -665,4 +666,4 @@ module.exports = (swagger, v2) ->
     swagger["add#{route.spec.method}"](route);true
 
 
-  swagger.configure("#{nconf.get('BASE_URL')}/api/v2", "2")
+  swagger.configure("#{nconf.get('BASE_URL')}/api/v2", "2")