ci: implement basic GitHub CI script

The Travis CI appeared to be broken, and there is no need to continue
using the external service now that GitHub has one built in.

Author: everythingfunctional

.github/workflows/ci.yml

@@ -0,0 +1,32 @@
+name: CI
+
+on: push
+
+jobs:
+  Build:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: true
+
+    env:
+      FC: gfortran
+      GCC_V: 10
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+
+    - name: Install Dependencies
+      run: |
+        sudo apt install -y gfortran-${GCC_V} cmake mpich
+        sudo update-alternatives --install /usr/bin/gfortran gfortran /usr/bin/gfortran-${GCC_V} 100
+
+    - name: Build and Test
+      run: |
+        mkdir build
+        cd build
+        cmake -Wdev -DCMAKE_INSTALL_PREFIX:PATH="${HOME}/OpenCoarrays" -DCMAKE_BUILD_TYPE:STRING="Debug" ..
+        make -j $(nproc)
+        ctest --output-on-failure --schedule-random --repeat-until-fail 1 --timeout 200
+        make install
+        make uninstall