Use GH Actions

This migrates to a more accessible platform

Author: zpao

.github/workflows/ci.yml

@@ -0,0 +1,29 @@
+name: CI
+on:
+  - push
+  - pull_request
+
+jobs:
+  ci:
+    name: "Build & Test (React v${{ matrix.react_version}})"
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        react_version:
+          - "0.14.9"
+          - "15.0"
+          - "15"
+          - "16.0"
+          - "16"
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-node@v2
+      with:
+        node-version: "lts/*"
+        cache: 'yarn'
+    - run: yarn install
+    - run: yarn add react@${{ matrix.react_version }}
+    - run: yarn list --pattern 'react'
+    - run: yarn run pretest
+    - run: yarn run tests-only
+    - run: yarn run build