Improved version of express middleware with tests.

Implemented working solution to express middleware that works for
both GET and POST requests.

Updated README with express middleware usage doc.

Completed tests for middleware
This code is a little hard to read. I would go with:

      var data, url, host;

      // Prepare the data -- this will depend on the method
      if( req.method === 'GET' ){
        var u = require( 'url').parse( req.url, true );
        data = u.query;
        url = req.protocol + '://' + req.headers.host + u.pathname;
      } else if( req.method === 'POST' ) {
        url = req.protocol + '://' + req.headers.host + req.url;
        var data = req.body;
      } else {
        next( new Error("HTTP method not supported"));
      }