Migrate CI build to GitHub Actions (#102)

* Migrate CI build to GitHub Actions
* Build on all branches (to debug on fork)
* Java 9 and above are not supported

.github/workflows/ci.yml

@@ -0,0 +1,25 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - '*'
+  pull_request:
+    branches:
+      - '*' 
+
+jobs:
+  build:
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+        java-version: [7, 8]
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Java ${{ matrix.java-version }}
+      uses: actions/setup-java@v1
+      with:
+        java-version: ${{ matrix.java-version }}
+    - name: Build with Maven
+      run: mvn verify