Breaking: drop node 6 and 8 (Level/community#98)

Author: vweevers

.travis.yml

@@ -1,9 +1,9 @@
 language: node_js
 
 node_js:
-  - 6
-  - 8
   - 10
+  - 12
+  - 14
 
 after_success: npm run coverage
 

package.json

@@ -37,6 +37,6 @@
     "level"
   ],
   "engines": {
-    "node": ">=6"
+    "node": ">=10"
   }
 }