👷 removed retired images...

👷 removed retired images (https://blog.travis-ci.com/2016-11-17-retiring-some-osx-images/)

.travis.yml

@@ -104,32 +104,20 @@ matrix:
 
   # OSX / Clang
 
-  - os: osx
-    osx_image: beta-xcode6.1
-
-  - os: osx
-    osx_image: beta-xcode6.2
-
-  - os: osx
-    osx_image: beta-xcode6.3
-
   - os: osx
     osx_image: xcode6.4
 
   - os: osx
-    osx_image: xcode7.1
+    osx_image: xcode7.3
 
   - os: osx
-    osx_image: xcode7.2
+    osx_image: xcode8
 
   - os: osx
-    osx_image: xcode7.3
-
-  #- os: osx
-  #  osx_image: xcode8
+    osx_image: xcode8.1
 
   - os: osx
-    osx_image: xcode8.1
+    osx_image: xcode8.2
 
   # Linux / GCC