build: support Node.js 4.x

Author: dougwilson

.travis.yml

@@ -6,6 +6,7 @@ node_js:
   - "1.8"
   - "2.5"
   - "3.3"
+  - "4.2"
 sudo: false
 before_install:
   # Setup Node.js version-specific dependencies

appveyor.yml

@@ -6,6 +6,7 @@ environment:
     - nodejs_version: "1.8"
     - nodejs_version: "2.5"
     - nodejs_version: "3.3"
+    - nodejs_version: "4.2"
 install:
   - ps: Install-Product node $env:nodejs_version
   - if "%nodejs_version%" equ "0.8" npm rm --save-dev istanbul