various fixes

.travis.yml

@@ -4,7 +4,6 @@ sudo: required
 branches:
   only:
     - develop
-    - travis
 
 matrix:
   include:
@@ -49,27 +48,21 @@ matrix:
 
     # MAC
     - os: osx
-      osx_image: xcode8.1
+      osx_image: xcode8  # currently macOS 10.11 (>= xcode8.1) doesn't support electron-builder codesigning (https://github.com/electron-userland/electron-builder/issues/820#issuecomment-267777060)
       env:
           - GULP_PLATFORM=mac
       node_js: 6
       before_install:
         - brew update
         - brew install gnu-tar libicns graphicsmagick xz
-        - npm install -g gulp yarn
+        - npm install -g gulp
 
 cache:
   yarn: true
-  directories:
-    - node_modules
-    - app/node_modules
-    - $HOME/.electron
-    - $HOME/.cache
 
 install:
   - PATH=$PATH:$HOME/.meteor && curl -L https://raw.githubusercontent.com/arunoda/travis-ci-meteor-packages/master/configure.sh | /bin/sh
   - npm install -g meteor-build-client electron@1.3.5
-  - yarn
 
 script:
   - travis_wait 60 gulp mist --platform $GULP_PLATFORM