build: Test Node.js versions to 6, 8 and 10

Krinkle · Krinkle · commit 975f99edfe53 · 2019-03-02T00:10:03.000Z
Remove testing of Node.js versions that are no longer supported.
diff --git a/.travis.yml b/.travis.yml
@@ -1,6 +1,5 @@
-sudo: false
 language: node_js
 node_js:
-  - '7'
-  - '6'
-  - '4.1.1'
+  - 10
+  - 8
+  - 6
