fix: Don't use global URL in plugin (#80)

* fix: import URL explicitly to work in node 8

* fix: rely on error code, add node 8 to travis

* fix: always suppress the error

Author: ilyamkin

.travis.yml

@@ -4,6 +4,7 @@ cache: npm
 notifications:
   email: false
 node_js:
+  - '8'
   - '10'
   - '12'
 install: npm install

src/index.js

@@ -1,3 +1,4 @@
+import { URL } from 'url';
 import visit from 'unist-util-visit';
 
 import { defaultTransformers } from './transformers';