Switch from Travis-CI to GitHub actions (#1286)

Travis-CI is dead. GitHub actions is the new hotness.
The minimally supported version is Go1.11 to make use of modules.
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..bd97bd4
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,22 @@
+on: [push, pull_request]
+name: Test
+jobs:
+  test:
+    strategy:
+      matrix:
+        go-version: [1.11.x, 1.12.x, 1.13.x, 1.14.x, 1.15.x, 1.16.x]
+        os: [ubuntu-latest, macos-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: Install Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: ${{ matrix.go-version }}
+    - name: Checkout code
+      uses: actions/checkout@v2
+    - name: TestLatest
+      if: matrix.go-version == '1.16.x'
+      run: ./test.bash
+    - name: TestAll
+      if: matrix.go-version != '1.16.x'
+      run: go test ./...
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 0b51666..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,22 +0,0 @@
-language: go
-before_install:
-  - mkdir /tmp/go1.12
-  - curl -L -s https://dl.google.com/go/go1.12.linux-amd64.tar.gz | tar -zxf - -C /tmp/go1.12 --strip-components 1
-  - unset GOROOT
-  - (GO111MODULE=on /tmp/go1.12/bin/go mod vendor)
-matrix:
-  include:
-    - go: 1.9.x
-      script: go test -tags protolegacy -v ./...
-    - go: 1.10.x
-      script: go test -tags protolegacy -v ./...
-    - go: 1.11.x
-      script: go test -tags protolegacy -v ./...
-    - go: 1.12.x
-      script: go test -tags protolegacy -v ./...
-    - go: 1.13.x
-      script: go test -tags protolegacy -v ./...
-    - go: 1.14.x
-      script: go test -tags protolegacy -v ./...
-    - go: 1.15.x
-      script: ./test.bash