Add travis config file

.travis.yml

+language: node_js
+node_js:
+- '4'
+- '6'
+env:
+  - CXX=g++-4.8
+cache:
+  directories:
+  - node_modules
+addons:
+  apt:
+    sources:
+    - ubuntu-toolchain-r-test
+    packages:
+    - gcc-4.8
+    - g++-4.8
+notifications:
+  slack: busytalk:mjQOgfT3qFIhFmy0a7TuEYaf
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