include request module version in default http agent string

lib/uristream.js

@@ -19,7 +19,7 @@ try {
 function noop() {};
 
 var pkg = require('../package');
-var DEFAULT_AGENT = util.format('%s/v%s (http://github.com/kanongil/node-hls-tools) node.js/%s', pkg.name, pkg.version, process.version);
+var DEFAULT_AGENT = util.format('%s/v%s (http://github.com/kanongil/node-hls-tools) request/v%s node.js/%s', pkg.name, pkg.version, require('request/package').version, process.version);
 
 module.exports = uristream;
 uristream.UriFetchStream = UriFetchStream;