Update Travis CI to Ubuntu 16.04

Rollback Appveyor CI from Node 8 to 7

.travis.yml

@@ -1,21 +1,27 @@
 language: node_js
-node_js:
-  - "4"
-  - "6"
-  - "8"
-os:
-  - linux
-  - osx
+matrix:
+  include:
+    - os: linux
+      dist: trusty
       sudo: false
-addons:
-  apt:
-    sources:
-    - ubuntu-toolchain-r-test
-    packages:
-    - g++-4.8
+      node_js: "4"
+    - os: linux
+      dist: trusty
+      sudo: false
+      node_js: "6"
+    - os: linux
+      dist: trusty
+      sudo: false
+      node_js: "8"
+    - os: osx
       osx_image: xcode8
-before_install:
-  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then export CXX=g++-4.8; fi
+      node_js: "4"
+    - os: osx
+      osx_image: xcode8
+      node_js: "6"
+    - os: osx
+      osx_image: xcode8
+      node_js: "8"
 after_success:
   - npm install coveralls
   - cat ./coverage/lcov.info | ./node_modules/coveralls/bin/coveralls.js

appveyor.yml

@@ -6,7 +6,7 @@ environment:
   matrix:
   - nodejs_version: "4"
   - nodejs_version: "6"
-  - nodejs_version: "8"
+  - nodejs_version: "7"
 install:
   - ps: Install-Product node $env:nodejs_version x64
   - npm install -g npm@latest