chore: drop node 6 and 8 support (#69)

diff --git a/.travis.yml b/.travis.yml
index 5163e1f..2948c2b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -24,8 +24,6 @@
   - windows
 
 node_js:
-  - 6
-  - 8
   - 10
   - 12
 
diff --git a/package.json b/package.json
index ae8a38d..ac9ed8f 100644
--- a/package.json
+++ b/package.json
@@ -56,7 +56,7 @@
   ],
   "license": "Apache-2.0",
   "engines": {
-    "node": ">=6.0.0"
+    "node": ">=10.0.0"
   },
   "nyc": {
     "include": [