Add travis-ci integration

Author: Erik Rigtorp

.travis.yml

@@ -0,0 +1,103 @@
+language: cpp
+
+sudo: false
+
+matrix:
+  include:
+
+    # clang-4
+    - env: COMPILER=clang++-4.0
+      compiler: clang
+      os: linux
+      addons:
+        apt:
+          packages:
+            - clang-4.0
+            - libstdc++-6-dev
+            - libsparsehash-dev
+          sources:
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-trusty-4.0
+
+    # clang-5
+    - env: COMPILER=clang++-5.0
+      compiler: clang
+      os: linux
+      addons:
+        apt:
+          packages:
+            - clang-5.0
+            - libstdc++-7-dev
+            - libsparsehash-dev
+          sources:
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-trusty-5.0
+
+    # clang-6
+    - env: COMPILER=clang++-6.0
+      compiler: clang
+      os: linux
+      addons:
+        apt:
+          packages:
+            - clang-6.0
+            - libstdc++-7-dev
+            - libsparsehash-dev
+          sources:
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-trusty-6.0
+
+    # gcc-5
+    - env: COMPILER=g++-5
+      compiler: gcc
+      os: linux
+      addons:
+        apt:
+          packages:
+            - g++-5
+            - libsparsehash-dev
+          sources:
+            - ubuntu-toolchain-r-test
+
+    # gcc-6
+    - env: COMPILER=g++-6
+      compiler: gcc
+      os: linux
+      addons:
+        apt:
+          packages:
+            - g++-6
+            - libsparsehash-dev
+          sources:
+            - ubuntu-toolchain-r-test
+
+    # gcc-7
+    - env: COMPILER=g++-7
+      compiler: gcc
+      os: linux
+      addons:
+        apt:
+          packages:
+            - g++-7
+            - libsparsehash-dev
+          sources:
+            - ubuntu-toolchain-r-test
+
+    # gcc-8
+    - env: COMPILER=g++-8
+      compiler: gcc
+      os: linux
+      addons:
+        apt:
+          packages:
+            - g++-8
+            - libsparsehash-dev
+          sources:
+            - ubuntu-toolchain-r-test
+
+before_script:
+  - export CXX=$COMPILER
+  - ./gradlew
+
+script:
+  - ./cppbuild/cppbuild