ci: sudo is required.

.travis.yml

@@ -3,13 +3,13 @@ compiler:
   - gcc
   - clang
 before_script:
-  - apt-get install -y cmake
+  - sudo apt-get install -y cmake
   - wget https://github.com/google/googletest/archive/release-1.8.0.zip
   - unzip -q release-1.8.0.zip
   - cd googletest-release-1.8.0
   - cmake .
   - make
-  - make install
+  - sudo make install
   - cd ..
 script:
   - cd examples