Drop node < 4 (#358)

Author: hzoo

.travis.yml

@@ -2,23 +2,8 @@ git:
   depth: 1
 sudo: false
 language: node_js
-before_install:
-  - sh -c "if [ '$ESLINT_VERSION' = '2' ]; then npm i --save-dev eslint@2; fi"
 matrix:
   include:
-    - node_js: "0.10"
-      env: ESLINT_VERSION=2
-    - node_js: "0.12"
-      env: ESLINT_VERSION=2
     - node_js: "4"
-      env: ESLINT_VERSION=2
-    - node_js: "4"
-      env: ESLINT_VERSION=3
-    - node_js: "5"
-      env: ESLINT_VERSION=2
     - node_js: "5"
-      env: ESLINT_VERSION=3
-    - node_js: "6"
-      env: ESLINT_VERSION=2
     - node_js: "6"
-      env: ESLINT_VERSION=3

package.json

@@ -29,6 +29,9 @@
   },
   "author": "Sebastian McKenzie <[email protected]>",
   "license": "MIT",
+  "engines": {
+    "node": ">=4"
+  },
   "bugs": {
     "url": "https://github.com/babel/babel-eslint/issues"
   },