Travis: install more recent cmake on linux.

Author: jgm

.travis.yml

@@ -23,6 +23,20 @@ before_install:
      then
          echo "Building without python3, to make sure that works."
      fi
+ - |
+     if ( test "`uname -s`" = "Darwin" )
+     then
+       #cmake v2.8.12 is installed on the Mac workers now
+       #brew update
+       #brew install cmake
+       echo
+     else
+       #install a newer cmake since at this time Travis only has version 2.8.7
+       echo "yes" | sudo add-apt-repository ppa:kalakris/cmake
+       sudo apt-get update -qq
+       sudo apt-get install cmake
+     fi
+
 script:
  - make
  - make test