Drop support for non-active lts and current release

Closes #649

.travis.yml

@@ -1,6 +1,8 @@
-language: node_js
-node_js:
-  - "0.10"
-  - node
-  - iojs
 sudo: false
+
+language: node_js
+
+node_js:
+  - lts/boron
+  - lts/carbon
+  - current

README.md

@@ -4,6 +4,12 @@ Sass plugin for [Gulp](https://github.com/gulpjs/gulp).
 
 **_Before filing an issue, please make sure you have [Updated to the latest Gulp Sass](https://github.com/dlmanning/gulp-sass/wiki/Update-to-the-latest-Gulp-Sass) and have gone through our [Common Issues and Their Fixes](https://github.com/dlmanning/gulp-sass/wiki/Common-Issues-and-Their-Fixes) section._**
 
+# Support
+
+Only [Active LTS and Current releases][1] are supported.
+
+[1]: https://github.com/nodejs/Release#release-schedule
+
 # Install
 
 ```

appveyor.yml

@@ -11,12 +11,9 @@ platform:
 
 environment:
   matrix:
-    - nodejs_version: 0.10
-    - nodejs_version: 0.12
-    - nodejs_version: 4
-    - nodejs_version: 6
-    - nodejs_version: 8
-    - nodejs_version: 9
+    - nodejs_version: lts/boron
+    - nodejs_version: lts/carbon
+    - nodejs_version: current
 
 install:
   - ps: Install-Product node $env:nodejs_version $env:platform

package.json

@@ -3,6 +3,9 @@
   "version": "3.2.1",
   "description": "Gulp plugin for sass",
   "main": "index.js",
+  "engines": {
+    "node": ">=6"
+  },
   "scripts": {
     "test": "./node_modules/.bin/mocha test"
   },