Add appveyor build for Node 5.0 (ABI 47)

Closes node-usb#102

Author: kevinmehall

appveyor.yml

@@ -13,6 +13,7 @@ environment:
     - node_version: '2.5'
     - node_version: '3.3'
     - node_version: '4.1'
+    - node_version: '5.0'
 
 install:
   - ps: Install-Product node $env:node_version $env:platform