Migrate to GitHub Actions for CI (#259)

Goal: get the CI integration up and running again.
Progress: Got the unit and lint tests passing. 
Incomplete and putting out of scope: integration test and release functionality. 
  - the integration test stalled at the 20m and eventually timed out. I'm leaving it in, albeit commented out, to make it easier for the next attempter given it does actually run.
  - the release I'm leaving out entirely as I don't intend to make a new release, I just want to make enough progress to have tests execute for #258

Motivation: Upgrade kubenetes artifacts to handle version 1.22.

.github/workflows/actions.yml

@@ -1,6 +1,73 @@
-on: [push, pull_request]
+name: checks
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
 jobs:
-  update-ci:
-    runs-on: ubuntu-latest
+  unit-tests:
+    runs-on: ubuntu-18.04
+    defaults:
+      run:
+        working-directory: go/src/github.com/lyft/flinkk8soperator
+    env:
+      GOPATH: "/home/runner/work/flinkk8soperator/flinkk8soperator/go/"
     steps:
-      - run: echo "CI is no longer running on this repo, update the files in .github/workflows to re-enable it. See the .travis.yml file for your previous CI config"; exit 1
+      - name: checkout
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 1
+          path: go/src/github.com/lyft/flinkk8soperator
+      - name: install go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.12
+      - name: install
+        run: make install
+      - name: test
+        run: make test_unit
+  lint:
+    runs-on: ubuntu-18.04
+    defaults:
+      run:
+        working-directory: go/src/github.com/lyft/flinkk8soperator
+    env:
+      GOPATH: "/home/runner/work/flinkk8soperator/flinkk8soperator/go/"
+    steps:
+      - name: checkout
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 1
+          path: go/src/github.com/lyft/flinkk8soperator
+      - name: install go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.12
+      - name: install
+        run: make install
+      - name: test
+        run: make lint
+  # TODO: restore this test
+  # integration-tests:
+  #   runs-on: ubuntu-18.04
+  #   defaults:
+  #     run:
+  #       working-directory: go/src/github.com/lyft/flinkk8soperator
+  #   env:
+  #     GOPATH: "/home/runner/work/flinkk8soperator/flinkk8soperator/go/"
+  #   steps:
+  #     - name: checkout
+  #       uses: actions/checkout@v2
+  #       with:
+  #         fetch-depth: 1
+  #         path: go/src/github.com/lyft/flinkk8soperator
+  #     - name: install go
+  #       uses: actions/setup-go@v2
+  #       with:
+  #         go-version: 1.12
+  #     - name: install
+  #       run: integ/install.sh
+  #     - name: setup
+  #       run: integ/setup.sh
+  #     - name: test
+  #       run: sudo "PATH=$PATH" "GOPATH=$GOPATH" integ/test.sh