[Tests] up to node v8.8

Author: ljharb

.travis.yml

@@ -2,7 +2,7 @@ language: node_js
 os:
  - linux
 node_js:
-  - "8.6"
+  - "8.8"
   - "7.10"
   - "6.11"
   - "5.12"
@@ -30,6 +30,10 @@ matrix:
   include:
     - node_js: "node"
       env: COVERAGE=true
+    - node_js: "8.7"
+      env: TEST=true ALLOW_FAILURE=true
+    - node_js: "8.6"
+      env: TEST=true ALLOW_FAILURE=true
     - node_js: "8.5"
       env: TEST=true ALLOW_FAILURE=true
     - node_js: "8.4"