Enable OSX on Travis (#111)

* Add OSX to Travis

* Installing gcc-48 should not be needed

Author: Lars-Magnus Skog

.travis.yml

@@ -2,18 +2,9 @@ sudo: false
 
 language: node_js
 
-env:
-  - CXX=g++-4.8
-
-addons:
-  apt:
-    sources:
-      - ubuntu-toolchain-r-test
-    packages:
-      - g++-4.8
-
-before_install:
-  - export JOBS=max
+os:
+  - osx
+  - linux
 
 node_js:
   - 6