remove support for v0.10, v0.12, v1, v2, v3

Author: JacksonTian

.travis.yml

@@ -1,13 +1,8 @@
 sudo: false
 language: node_js
 node_js:
-  - '5'
+  - '6'
   - '4'
-  - '3'
-  - '2'
-  - '1'
-  - '0.12'
-  - '0.10'
 script:
   - "npm run ci"
 after_script:

package.json

@@ -51,6 +51,6 @@
     "should": "5"
   },
   "engines": {
-    "node": ">= 0.10.0"
+    "node": ">= 4"
   }
 }