Drop node 4 (#11)

* Drop node 4

* upgrade to babel 7

Author: SimenB

.babelrc

@@ -1,11 +1,10 @@
 {
   "presets": [
     [
-      "env",
+      "@babel/preset-env",
       {
-        "useBuiltIns": true,
         "targets": {
-          "node": "4"
+          "node": "6"
         }
       }
     ]

.travis.yml

@@ -2,4 +2,4 @@ language: node_js
 node_js:
   - "8"
   - "6"
-  - "4"
+  - "10"

package.json

@@ -23,19 +23,19 @@
     "throat": "^4.1.0"
   },
   "devDependencies": {
-    "babel-cli": "^6.26.0",
-    "babel-core": "^6.26.0",
-    "babel-jest": "^21.0.0",
-    "babel-polyfill": "^6.26.0",
-    "babel-preset-env": "^1.6.0",
+    "@babel/cli": "^7.0.0-beta.46",
+    "@babel/core": "^7.0.0-beta.46",
+    "@babel/preset-env": "^7.0.0-beta.46",
+    "babel-core": "^7.0.0-0",
+    "babel-jest": "^22.4.3",
     "eslint": "^4.5.0",
     "eslint-config-airbnb-base": "^12.1.0",
     "eslint-config-prettier": "^2.3.0",
     "eslint-plugin-import": "^2.7.0",
     "eslint-plugin-jest": "^21.15.1",
     "eslint-plugin-prettier": "^2.2.0",
     "execa": "^0.10.0",
-    "jest": "^21.0.2",
+    "jest": "^22.4.3",
     "prettier": "^1.7.4"
   }
 }