Use travis bionic image

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

.travis.yml

@@ -39,18 +39,17 @@ jobs:
         - cmake .
         - make
         - make test
-    - dist: xenial
+    - 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:
-        - sudo docker run -it --rm -v ${TRAVIS_BUILD_DIR}:/repo ubuntu:bionic /bin/bash -c "
-          set -e
-          export DEBIAN_FRONTEND=noninteractive
-          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
-          cd /repo
-          cmake --version
-          cmake .
-          make
-          make test"
+        - cd ${TRAVIS_BUILD_DIR}
+        - cmake --version
+        - cmake .
+        - make
+        - make test