BREAKING CHANGE: Require Node 8+ (and upgrade yargs)

Node 6 reached end of life earlier this year: https://nodejs.org/en/about/releases/

Closes Javascipt#20

Author: paulmelnikow

.travis.yml

@@ -1,10 +1,9 @@
 sudo: false
 language: node_js
 node_js:
-  - '4'
-  - '6'
-  - '7'
   - '8'
-  - '9'
+  - '10'
+  - '11'
+  - '12'
 before_script: npm link
-script: jsome package.json && cat package.json | jsome && npm test
+script: jsome package.json && cat package.json | jsome && npm test

package.json

@@ -28,7 +28,7 @@
   "dependencies": {
     "chalk": "^2.3.0",
     "json-stringify-safe": "^5.0.1",
-    "yargs": "^11.0.0"
+    "yargs": "^13.2.4"
   },
   "bin": {
     "jsome": "./bin/cli.js"
@@ -40,6 +40,9 @@
     "jest": "^21.2.1",
     "jsesc": "^2.5.1"
   },
+  "engines": {
+    "node": ">= 8"
+  },
   "jest": {
     "testEnvironment": "node"
   }