ci(travis): upgrade to node 8
diff --git a/.travis.yml b/.travis.yml
index 909db23..ec92f48 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,12 +12,12 @@
 env:
   global:
     - SAUCE_USERNAME=snay
-    - TRAVIS_NODE_VERSION=6
+    - TRAVIS_NODE_VERSION=8
     - ANDROID_API_LEVEL=28
     - ANDROID_BUILD_TOOLS_VERSION=28.0.3
 
 language: node_js
-node_js: 6
+node_js: 8
 
 # yaml anchor/alias: https://medium.com/@tommyvn/travis-yml-dry-with-anchors-8b6a3ac1b027