enable windows CI

Author: stefanpenner

.travis.yml

@@ -2,7 +2,11 @@ language: node_js
 node_js:
   - "10"
 os:
-  # - windows # TODO: make this work
+  - windows
   - linux
 cache:
   yarn: true
+
+before_install:
+  # work around due to the following error: tar: C\:\\Users\travis\\AppData\\Local\\Yarn\\Cache: Cannot stat: No such file or directory
+  - if [[ "$TRAVIS_OS_NAME" == "windows" ]]; then mkdir -p /Users/travis/AppData/Local/Yarn/Cache:; fi