New: Enable OSX builds with Travis (#497)

.travis.yml

@@ -1,13 +1,18 @@
 language: csharp
+os:
+  - linux
+  - osx
 solution: src/Lidarr.sln
-install:
+before_install:
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install yarn; fi
   - nvm install 8
   - nvm use 8
 script:
-  - node --version
   - ./build.sh
   - chmod +x test.sh
   - ./test.sh Linux Unit
 after_success:
   - chmod +x package.sh
   - ./package.sh
+