fix: Add support for Node 4 (#286)

Closes #285 
Fixes #236

.babelrc

@@ -2,7 +2,7 @@
   "presets": [
     ["env", {
       "targets": {
-        "node": 6
+        "node": 4
       },
       "loose": true,
       "useBuiltIns": true

.circleci/config.yml

@@ -1,5 +1,16 @@
 version: 2
 jobs:
+  test_with_node_4:
+    docker:
+      - image: circleci/node:4
+    steps:
+      - checkout
+      - run:
+          name: Install dependencies
+          command: npm install
+      - run:
+          name: Test
+          command: npm test
   test_with_node_6:
     docker:
       - image: circleci/node:6
@@ -40,6 +51,7 @@ workflows:
   version: 2
   test_all:
     jobs:
+      - test_with_node_4
       - test_with_node_6
       - test_with_node_8
       - test_with_node_9

appveyor.yml

@@ -1,5 +1,6 @@
 environment:
   matrix:
+    - nodejs_version: '4'
     - nodejs_version: '6'
     - nodejs_version: '8'
     - nodejs_version: '9'

package.json

@@ -8,7 +8,7 @@
     "url": "https://github.com/tleunen/babel-plugin-module-resolver.git"
   },
   "engines": {
-    "node": ">= 6.0.0"
+    "node": ">= 4.0.0"
   },
   "files": ["lib"],
   "author": {
@@ -72,6 +72,7 @@
     "*.{js}": ["prettier-eslint --write", "eslint --fix", "git add"]
   },
   "jest": {
+    "testEnvironment": "node",
     "testRegex": "/test/.*\\.test\\.js$",
     "collectCoverageFrom": ["src/**/*.js", "!src/log.js"]
   }