chore: test node 10 to 12 (#48)

diff --git a/.travis.yml b/.travis.yml
index b9af4c5..e96658d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,4 +1,5 @@
 language: node_js
 sudo: false
 node_js:
-  - "4.2"
+  - "10"
+  - "12"