Try to update cmake on Mac travis.

travis_cmake_linux.sh

@@ -1,5 +1,2 @@
 #!/bin/bash
-sudo rm -rf /usr/local/cmake-3.9.2 && sudo rm -rf /usr/local/cmake
+ls /Applications
-wget https://cmake.org/files/v3.12/cmake-3.12.0-rc2-Linux-x86_64.sh
-chmod +x cmake-3.12.0-rc2-Linux-x86_64.sh
-sudo ./cmake-3.12.0-rc2-Linux-x86_64.sh --skip-license --exclude-subdir --prefix=/usr/local