allow PATCH verb to be processed by the ruby application


the HTTP PATCH verb works with RackServlet but with RackFilter the filter chain returns 501 on those verbs and 501 is considered as handled and will not be processed by the ruby application. this patch adds 501 to the list of responses for which the request will be passed on to the ruby application.

the patch is particular important for rich client using rest(ful) API servers. the PATCH allows to partially updated resources on the server whereas PUT is meant to sent the full object over the wire.

Sponsored by: Lookout, Inc.