drop support of node 6

Signed-off-by: Anton Kosiakov <anton.kosyakov@typefox.io>

.travis.yml

@@ -1,5 +1,5 @@
 language: node_js
-os: linux
+node_js: '8'
 git:
   depth: 1
 cache:
@@ -42,12 +42,10 @@ jobs:
   allow_failures:
     - os: osx
   include:
-  - stage: test
-    node_js: '6'
-  - stage: test
-    node_js: '8'
+  - state: test
+    os: linux
   - stage: deploy
-    node_js: '6'
+    os: linux
     before_script: skip
     script: skip
     install: skip
@@ -60,8 +58,7 @@ jobs:
       on:
         branch: master
       skip_cleanup: true
-  - stage: slow test
-    node_js: '8'
+  - stage: OSx test
     os: osx
     env: CXX=c++
     before_script: skip

doc/Developing.md

@@ -37,7 +37,7 @@ For Windows instructions [click here](#building-on-windows).
      - [Root privileges errors](#root-privileges-errors)
 
 ## Prerequisites
- - Node.js v6.0 or higher
+ - Node.js v8.0 or higher
  - [Yarn package manager](https://yarnpkg.com/en/docs/install)
  - git