Increase convenience of query members (#36)

Author: ferhatelmas

README.md

@@ -132,7 +132,7 @@ chan.unban_user('bob-1')
 chan.query({'messages' => { 'limit' => 10, 'id_lte' => m1['id']}})
 
 # Query channel members
-chan.query_members({name: {'$autocomplete': 'test'}}, {last_created_at: -1}, offset: 5, limit: 5)
+chan.query_members({name: {'$autocomplete': 'test'}}, sort: {last_created_at: -1}, offset: 5, limit: 5)
 ```
 
 ### Messages

lib/stream-chat/channel.rb

@@ -61,7 +61,7 @@ def query(**options)
       state
     end
 
-    def query_members(filter_conditions: {}, sort: nil, **options)
+    def query_members(filter_conditions = {}, sort: nil, **options)
       params = {}.merge(options).merge({
                                          id: @id,
                                          type: @channel_type,