update ci configs.

Author: ctalkington

.travis.yml

@@ -1,6 +1,7 @@
 sudo: false
 language: node_js
 node_js:
+  - 8
   - 6
   - 4
   - '0.12'

appveyor.yml

@@ -1,13 +1,14 @@
 environment:
   matrix:
+    - nodejs_version: '8'
     - nodejs_version: '6'
     - nodejs_version: '4'
     - nodejs_version: '0.12'
     - nodejs_version: '0.10'
 install:
   - ps: Install-Product node $env:nodejs_version
   - set CI=true
-  - npm -g install npm@latest
+  - IF %nodejs_version% LSS 4 npm -g install npm@2
   - set PATH=%APPDATA%\npm;%PATH%
   - npm install
 matrix: