Add apt-gets for gflags, gtest

.travis.yml

 language: cpp
+before_install:
+  - sudo add-apt-repository ppa:yjwong/gflags -y
+  - sudo apt-get update -qq
+  - sudo apt-get install -qq libgtest-dev libgflags-dev
 script: ./tools/run_tests/run_tests.py -l c c++ -t -j2
 notifications:
   email: false