force_status_check param is dropped for source update

There is a force_status_check param in http://context.io/docs/2.0/accounts/sources#id-post

However, the update method in source.rb doesn't have it listed in the updatable_attributes 

https://github.com/contextio/contextio-ruby/blob/master/lib/contextio/source.rb

````ruby
def update(options={})
      updatable_attrs = %w(status sync_period service_level password
                           provider_token provider_token_secret
                           provider_consumer_key)
````

and so it gets dropped. 

Just wondering if this is intentional? Otherwise, it should be added. Thanks