add nightly test workflow, rm appveyor and travis config

.github/workflows/cron.yaml

@@ -0,0 +1,42 @@
+# Run a nightly test against unpinned conda environment
+name: Cron
+
+on:
+  schedule:
+    - cron: "0 0 * * *"
+
+jobs:
+  test:
+    name: ${{ matrix.CONDA_ENV }}-test
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        CONDA_ENV: [unpinned, upstream]    
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Setup Miniconda
+        uses: conda-incubator/setup-miniconda@v2
+        with:
+          auto-update-conda: true
+          auto-activate-base: false
+          activate-environment: test_env
+          environment-file: ci/environment-${{ matrix.CONDA_ENV }}.yml
+
+      - name: Development Install intake-xarray
+        shell: bash -l {0}
+        run: |
+          python -m pip install --no-deps -e .
+          conda list
+
+      - name: Run Tests
+        shell: bash -l {0}
+        run: |
+          pytest --verbose --ignore=intake_xarray/tests/test_network.py
+
+      - name: Run Tests Requiring Network Connection
+        shell: bash -l {0}
+        run: |
+          pytest --verbose intake_xarray/tests/test_network.py

ci/environment-unpinned.yml

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+name: test_env
+channels:
+  - conda-forge
+dependencies:
+  - python
+  - aiohttp
+  - boto3
+  - flask
+  - h5netcdf
+  - intake
+  - netcdf4
+  - pip
+  - pydap
+  - pytest
+  - rasterio
+  - s3fs
+  - scikit-image
+  - xarray
+  - zarr
+  - pip:
+       - rangehttpserver
+       - moto[s3]