Adding a test for HTTP/2

I've never really worked with node before and not sure how to run these
e2e tests, but this is baed on the usage shown on the project's Github

https://github.com/stefanjudis/is-http2

package.json

@@ -20,6 +20,7 @@
     "debug": "^2.2.0",
     "dns-sync": "^0.1.3",
     "imap": "^0.8.17",
+    "is-http2": "^1.1.0",
     "mkdirp": "^0.5.1",
     "mocha": "^2.2.5",
     "nodemailer": "^2.4.2",

test/selfhost-digitalocean-filesystem-test.js

@@ -15,6 +15,7 @@ var AppStore = require('../appstore.js'),
     Cloudron = require('../cloudron.js'),
     common = require('../common.js'),
     digitalocean = require('../digitalocean.js'),
+    ishttp2 = require('is-http2'),
     mailer = require('../mailer.js'),
     rimraf = require('rimraf'),
     semver = require('semver'),
@@ -238,6 +239,19 @@ describe('Selfhost DigitalOcean with filesystem backend', function () {
         cloudron.checkAddons(cloudron.appFqdn(location), owner);
     });
 
+    it('can access app with http2', function () {
+        ishttp2(cloudron.appFqdn(location), { includeSpdy: true })
+            .then(function (result) {
+                assert(result.isHttp2, 'App was not served with HTTP/2');
+                if (result.supportedProtocols) {
+                    console.log(`Supported protocols: ${ result.supportedProtocols.join(' ') }`);
+                }
+            })
+            .catch(function (error) {
+                assert(false, 'Could not verify HTTP/2');
+            });
+    });
+
     it('can set appstore config', function () {
         var token = appStore.getAccessToken(owner);
         appStore.setCredentials(owner.password, token);