build: test against Node.js 8.x nightly

Author: dougwilson

.travis.yml

@@ -10,6 +10,13 @@ node_js:
   - "5.12"
   - "6.10"
   - "7.6"
+matrix:
+  include:
+    - node_js: "8.0"
+      env: "NVM_NODEJS_ORG_MIRROR=https://nodejs.org/download/nightly"
+  allow_failures:
+    # Allow the nightly installs to fail
+    - env: "NVM_NODEJS_ORG_MIRROR=https://nodejs.org/download/nightly"
 sudo: false
 cache:
   directories: