revert: pin Node.js 10.x version to 10.0.0

This reverts commit a36e257,
as it is no longer needed - the new Node.js version 10.2.0 has
fixed the problem we were experiencing on Node.js 10.1.0.

Author: bajtos

.travis.yml

@@ -2,8 +2,7 @@ sudo: false
 language: node_js
 node_js:
   - "8"
-  - "10.0.0" # Pinned to prevent warning "fs.promises API is experimental"
-             # Waiting for https://github.com/nodejs/node/pull/20632
+  - "10"
 
 os:
   - linux

appveyor.yml

@@ -1,7 +1,7 @@
 environment:
   matrix:
     - nodejs_version: "8"
-    - nodejs_version: "10.0.0"
+    - nodejs_version: "10"
 
 install:
   - ps: Install-Product node $env:nodejs_version