Allow any HTTP method

In doing some work with CORS and Backbone, I ran into a need for txroutes to support OPTIONS and PATCH.  I noticed that there were a [few other missing methods](http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol#Request_methods) like TRACE and CONNECT from HTTP/1.1.

Rather than hardcoding each method (which can technically be extended in cases like [WebDAV](https://en.wikipedia.org/wiki/WebDAV)), it seems to make more sense to just override the generic `render` method instead.