Add Node 7 as a supported environment

.travis.yml

 language: node_js
 node_js:
+  - "7"
   - "6"
   - "4"
   - "0.12"

appveyor.yml

@@ -43,6 +43,7 @@
       - nodejs_version: 4
       - nodejs_version: 5
       - nodejs_version: 6
+      - nodejs_version: 7
 
   install:
     - ps: Install-Product node $env:nodejs_version $env:platform
@@ -113,6 +114,7 @@
       - nodejs_version: 0.12
       - nodejs_version: 4
       - nodejs_version: 6
+      - nodejs_version: 7
 
   install:
     - ps: Install-Product node $env:nodejs_version $env:platform

lib/extensions.js

@@ -66,6 +66,7 @@ function getHumanNodeVersion(abi) {
     case 46: return 'Node.js 4.x';
     case 47: return 'Node.js 5.x';
     case 48: return 'Node.js 6.x';
+    case 51: return 'Node.js 7.x';
     default: return false;
   }
 }