Refactor travis.yml

Shorten by using matrix key and add -Werror compiler flag.

Signed-off-by: Jacob Perron <jacobmperron@gmail.com>

.travis.yml

@@ -2,16 +2,18 @@ sudo: required
 
 language: cpp
 
-services:
-  - docker
-
 compiler:
   - gcc
 
-jobs:
+matrix:
   include:
-    - stage: test
+    - os: linux
       dist: trusty
+    - os: linux
+      dist: xenial
+    - os: linux
+      dist: bionic
+
 before_install:
   - sudo apt-get update -qq
   - sudo apt-get install build-essential cmake libboost-system-dev libboost-thread-dev libgtest-dev
@@ -19,37 +21,10 @@ jobs:
   - sudo cmake CMakeLists.txt
   - sudo make
   - sudo cp *.a /usr/lib
+
 script:
   - cd ${TRAVIS_BUILD_DIR}
   - cmake --version
-        - cmake .
-        - make
-        - make test
-    - dist: xenial
-      before_install:
-        - sudo apt-get update -qq
-        - sudo apt-get install build-essential cmake libboost-system-dev libboost-thread-dev libgtest-dev
-        - cd /usr/src/gtest
-        - sudo cmake CMakeLists.txt
-        - sudo make
-        - sudo cp *.a /usr/lib
-      script:
-        - cd ${TRAVIS_BUILD_DIR}
-        - cmake --version
-        - cmake .
-        - make
-        - make test
-    - dist: bionic
-      before_install:
-        - sudo apt-get update -qq
-        - sudo apt-get install build-essential cmake libboost-system-dev libboost-thread-dev libgtest-dev
-        - cd /usr/src/gtest
-        - sudo cmake CMakeLists.txt
-        - sudo make
-        - sudo cp *.a /usr/lib
-      script:
-        - cd ${TRAVIS_BUILD_DIR}
-        - cmake --version
-        - cmake .
+  - cmake -DCMAKE_CXX_FLAGS="-Werror" .
   - make
   - make test