Increase minimum Node version to 10

Node 8 has reached end-of-life.

Author: wimpyprogrammer

.travis.yml

@@ -1,7 +1,7 @@
 language: node_js
 node_js:
   - 'node'
-  - '8'
+  - '10'
 script:
   - npm run travisci
 cache:

package.json

@@ -15,7 +15,7 @@
   ],
   "sideEffects": false,
   "engines": {
-    "node": ">=8"
+    "node": ">=10"
   },
   "scripts": {
     "build": "npm run clean && babel src -d lib --extensions '.js,.ts' --ignore '**/*.spec.js','**/*.spec.ts' && npm run build-types",