Verify both cmake and stepmania install.

This comes from http://docs.travis-ci.com/user/installing-dependencies/

.install-cmake.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+set -ex
+wget http://www.cmake.org/files/v3.2/cmake-3.2.2.tar.gz
+tar -xzvf cmake-3.2.2.tar.gz
+cd cmake-3.2.2 && ./configure && make && sudo make install
+

.travis.yml

@@ -28,9 +28,7 @@ before_script:
     - sudo apt-get install -y libglu1-mesa-dev
     - sudo apt-get install -y mesa-common-dev
     - sudo apt-get install -y libglew-dev
-    - wget http://www.cmake.org/files/v3.2/cmake-3.2.2.tar.gz
-    - tar -xzvf cmake-3.2.2.tar.gz
-    - cd cmake-3.2.2 && ./configure && make && sudo make install
+    - ./.install-cmake.sh
 
 script:
     - cmake -G 'Unix Makefiles' . && cmake .