build: replace travis with github actions (#290)

Author: jrudolph

.github/workflows/validate.yml

@@ -0,0 +1,101 @@
+name: Test and publish
+
+on:
+  pull_request:
+  push:
+    branches: [ main ]
+    tags: [ v* ]
+
+jobs:
+  compile-and-test:
+    name: Compile and test and publish
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        scala-version:
+          - 2.11.6
+          - 2.11.7
+          - 2.11.8
+          - 2.11.11
+          - 2.11.12
+          - 2.12.3
+          - 2.12.4
+          - 2.12.5
+          - 2.12.6
+          - 2.12.7
+          - 2.12.8
+          - 2.12.9
+          - 2.12.10
+          - 2.12.11
+          - 2.12.12
+          - 2.12.13
+          - 2.12.14
+          - 2.13.0
+          - 2.13.1
+          - 2.13.2
+          - 2.13.3
+          - 2.13.4
+          - 2.13.5
+          - 2.13.6
+        jdk-version: [1.8, 1.11]
+        # some old scala versions don't support JDK 11
+        exclude:
+          - scala-version: 2.11.6
+            jdk-version: 1.11
+          - scala-version: 2.11.7
+            jdk-version: 1.11
+          - scala-version: 2.11.8
+            jdk-version: 1.11
+          - scala-version: 2.11.11
+            jdk-version: 1.11
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Checkout GitHub merge
+        if: github.event.pull_request
+        run: |-
+          git fetch origin pull/${{ github.event.pull_request.number }}/merge:scratch
+          git checkout scratch
+
+      - name: Set up JDK ${{ matrix.jdk-version }}
+        uses: olafurpg/setup-scala@v10
+        with:
+          java-version: adopt@${{ matrix.jdk-version }}
+
+      - name: Cache Coursier cache
+        uses: coursier/cache-action@v5
+
+      - name: Compile and test for JDK ${{ matrix.jdk-version }}, Scala ${{ matrix.scala-version }}
+        run: sbt -J-XX:ReservedCodeCacheSize=256M ++${{ matrix.scala-version }} test
+
+  publish:
+    name: Publish to Maven Central
+    if: startsWith(github.ref, 'refs/tags/v')
+    needs: [ compile-and-test ]
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Set up JDK 8
+        uses: olafurpg/setup-scala@v10
+        with:
+          java-version: [email protected]
+
+      - name: Cache Coursier cache
+        uses: coursier/cache-action@v5
+
+      - name: Publish
+        run: sbt ci-release
+        env:
+          PGP_SECRET: ${{ secrets.PGP_SECRET }}
+          SONATYPE_PASSWORD: ${{ secrets.SONATYPE_PASSWORD }}
+          SONATYPE_USERNAME: ${{ secrets.SONATYPE_USERNAME }}