OSX: update the Xcode versions

Author: Jared Grubb

.travis.yml

@@ -35,22 +35,28 @@ matrix:
           packages: ["clang-3.7", "cmake-data", "cmake"]
 
     - os: osx
-      osx_image: xcode6.4
+      osx_image: xcode9.4
       env:
-        - COMPILER=clang++ V='Apple LLVM 6.4'
-        - COMPILER=clang++ V='Apple LLVM 6.4' WITH_CPP14=true
+        - COMPILER=clang++ V='Apple LLVM 9.1'
+        - COMPILER=clang++ V='Apple LLVM 9.1' WITH_CPP14=true
 
     - os: osx
-      osx_image: xcode7
+      osx_image: xcode10.3
       env:
-        - COMPILER=clang++ V='Apple LLVM 7.0'
-        - COMPILER=clang++ V='Apple LLVM 7.0' WITH_CPP14=true
+        - COMPILER=clang++ V='Apple LLVM 10.0'
+        - COMPILER=clang++ V='Apple LLVM 10.0' WITH_CPP14=true
+    - os: osx
+      osx_image: xcode11.2
+      env:
+        - COMPILER=clang++ V='Apple LLVM 11.0'
+        - COMPILER=clang++ V='Apple LLVM 11.0' WITH_CPP14=true
 
 before_install:
-  - |
-    if [[ "${TRAVIS_OS_NAME}" == "osx" ]]; then
-      brew rm --force cmake && brew install cmake
-    fi
+  # - |
+  #   if [[ "${TRAVIS_OS_NAME}" == "osx" ]]; then
+  #     brew update
+  #     brew rm --force cmake && brew install cmake
+  #   fi
 
   - CMAKE_CXX_FLAGS+=" -Wall"