add Node.js 8 to Travis CI (#2086)

- explicitly terminate `test/jetstream.js` upon completion
- log verbose output from `test/benchmark.js` & `test/jetstream.js`
- remove obsolete workaround for Travis CI

test/jetstream.js

@@ -64,6 +64,7 @@ if (typeof phantom == "undefined") {
                     server.close();
                     if (code) throw new Error("JetStream failed!");
                     console.log("JetStream completed successfully.");
+                    process.exit(0);
                 });
             });
         }