add travis

Author: schickling

.travis.yml

@@ -7,7 +7,6 @@ env:
   global:
     - ELECTRON_CACHE=$HOME/.cache/electron
     - ELECTRON_BUILDER_CACHE=$HOME/.cache/electron-builder
-    - TEST_DIR=packages/graphql-playground-electron
 
 matrix:
   include:
@@ -28,6 +27,7 @@ before_install:
 
 script:
   - |
+    cd packages/graphql-playground-electron
     if [ "$TRAVIS_OS_NAME" == "linux" ]; then
       docker run --rm \
         --env-file <(env | grep -iE 'DEBUG|NODE_|ELECTRON_|YARN_|NPM_|CI|CIRCLE|TRAVIS|APPVEYOR_|CSC_|_TOKEN|_KEY|AWS_|STRIP|BUILD_') \