Replace Appveyor with Azure Pipelines in README and contributor guide (pydata#3052)

* Replace Appveyor with Azure Pipelines in README and contributor guide

* Delete coveralls upload

* doc note on auto-cancelling

Author: shoyer

README.rst

@@ -3,8 +3,8 @@ xarray: N-D labeled arrays and datasets
 
 .. image:: https://travis-ci.org/pydata/xarray.svg?branch=master
    :target: https://travis-ci.org/pydata/xarray
-.. image:: https://ci.appveyor.com/api/projects/status/github/pydata/xarray?svg=true&passingText=passing&failingText=failing&pendingText=pending
-   :target: https://ci.appveyor.com/project/shoyer/xray
+.. image:: https://dev.azure.com/xarray/xarray/_apis/build/status/pydata.xarray?branchName=master
+   :target: https://dev.azure.com/xarray/xarray/_build/latest?definitionId=1&branchName=master
 .. image:: https://coveralls.io/repos/pydata/xarray/badge.svg
    :target: https://coveralls.io/r/pydata/xarray
 .. image:: https://readthedocs.org/projects/xray/badge/?version=latest

ci/azure/unit-tests.yml

@@ -16,12 +16,6 @@ steps:
   # TODO: publish coverage results to Azure, once we can merge them across
   # multiple jobs: https://stackoverflow.com/questions/56776185
 
-- bash: |
-    source activate test_env
-    COVERALLS_REPO_TOKEN=$(coverallsToken) COVERALLS_PARALLEL=true coveralls
-  condition: succeededOrFailed()
-  displayName: Upload coverage to coveralls
-
 - task: PublishTestResults@2
   condition: succeededOrFailed()
   inputs:

doc/contributing.rst

@@ -384,12 +384,13 @@ Testing With Continuous Integration
 -----------------------------------
 
 The *xarray* test suite will run automatically on `Travis-CI <https://travis-ci.org/>`__,
-and `Appveyor <https://www.appveyor.com/>`__, continuous integration services, once
-your pull request is submitted. However, if you wish to run the test suite on a
-branch prior to submitting the pull request, then the continuous integration
-services need to be hooked to your GitHub repository. Instructions are here
-for `Travis-CI <http://about.travis-ci.org/docs/user/getting-started/>`__, and
-`Appveyor <https://www.appveyor.com/docs/>`__.
+and `Azure Pipelines <https://azure.microsoft.com/en-us/services/devops/pipelines//>`__,
+continuous integration services, once your pull request is submitted. However,
+if you wish to run the test suite on a branch prior to submitting the pull
+request, then the continuous integration services need to be hooked to your
+GitHub repository. Instructions are here for `Travis-CI
+<http://about.travis-ci.org/docs/user/getting-started/>`__, and
+`Azure Pipelines <https://docs.microsoft.com/en-us/azure/devops/pipelines/>`__.
 
 A pull-request will be considered for merging when you have an all 'green' build. If any
 tests are failing, then you will get a red 'X', where you can click through to see the
@@ -399,10 +400,9 @@ individual failed tests. This is an example of a green build.
 
 .. note::
 
-   Each time you push to your PR branch, a new run of the tests will be triggered on the CI.
-   Appveyor will auto-cancel any non-currently-running tests for that same pull-request.
-   You can also enable the auto-cancel feature for `Travis-CI here
-   <https://docs.travis-ci.com/user/customizing-the-build/#Building-only-the-latest-commit>`__.
+   Each time you push to your PR branch, a new run of the tests will be
+   triggered on the CI. If they haven't already finished, tests for any older
+   commits on the same branch will be automatically cancelled.
 
 .. _contributing.tdd: