test: run examples/externals on PRs too (#2559)

We run automated tests of IPFS examples & external repos on our
release branches, but there's no good reason not to run them on
every PR instead to give people early warning of breakages.

This PR changes the `.travis.yml` file to run all tests on every
submitted PR.

Author: achingbrain

package.json

@@ -19,5 +19,8 @@
     "libp2p-tcp": "~0.13.0",
     "libp2p-websocket-star": "~0.10.2",
     "pull-mplex": "~0.1.0"
+  },
+  "devDependencies": {
+    "execa": "^3.2.0"
   }
 }

test.js

@@ -16,8 +16,9 @@ const PeerBook = require('peer-book')
 async function test () {
   let output = ''
 
-  const proc = execa('node', [ path.join(__dirname, 'index.js') ], {
-    cwd: path.resolve(__dirname)
+  const proc = execa('node', [path.join(__dirname, 'index.js')], {
+    cwd: path.resolve(__dirname),
+    all: true
   })
   proc.all.on('data', async (data) => {
     process.stdout.write(data)