[appveyor.yml] update Appveyor configuration

Author: chrissimpkins

appveyor.yml

@@ -1,32 +1,14 @@
 environment:
   matrix:
-    - JOB: "3.5 64-bit"
-      PYTHON_HOME: "C:\\Python35-x64"
-      TOX_PY: py35
-
-    - JOB: "3.6 64-bit"
-      PYTHON_HOME: "C:\\Python36-x64"
+    - JOB: "3.6 32-bit"
+      PYTHON_HOME: "C:\\Python36"
       TOX_PY: py36
 
     - JOB: "3.7 64-bit"
       PYTHON_HOME: "C:\\Python37-x64"
       TOX_PY: py37
 
-    - JOB: "3.7 32-bit"
-      PYTHON_HOME: "C:\\Python37"
-      TOX_PY: py37
-
 install:
-  # If there is a newer build queued for the same PR, cancel this one.
-  # The AppVeyor 'rollout builds' option is supposed to serve the same
-  # purpose but it is problematic because it tends to cancel builds pushed
-  # directly to master instead of just PR builds (or the converse).
-  # credits: JuliaLang developers.
-  - ps: if ($env:APPVEYOR_PULL_REQUEST_NUMBER -and $env:APPVEYOR_BUILD_NUMBER -ne ((Invoke-RestMethod `
-        https://ci.appveyor.com/api/projects/$env:APPVEYOR_ACCOUNT_NAME/$env:APPVEYOR_PROJECT_SLUG/history?recordsNumber=50).builds | `
-        Where-Object pullRequestId -eq $env:APPVEYOR_PULL_REQUEST_NUMBER)[0].buildNumber) { `
-          throw "There are newer queued builds for this pull request, failing early." }
-
   # Prepend Python to the PATH of this build
   - "SET PATH=%PYTHON_HOME%;%PYTHON_HOME%\\Scripts;%PATH%"
 
@@ -35,12 +17,23 @@ install:
   - "python -c \"import struct; print(struct.calcsize('P') * 8)\""
 
   # upgrade pip and setuptools to avoid out-of-date warnings
-  - "python -m pip install --disable-pip-version-check --user --upgrade pip setuptools"
+  - "python -m pip install --disable-pip-version-check --user --upgrade pip setuptools virtualenv"
 
-  # install the test dependencies
-  - "python -m pip install tox"
+  # install the dependencies to run the tests
+  - "python -m pip install --upgrade tox pytest"
 
 build: false
 
-test_script: 
+# The following prevents Travis from running CI on pull requests that come from a
+# branch in the same repository. Without this, it will run the same CI for the
+# pull request branch _and_ the pull request itself, which makes no sense.
+branches:
+  only:
+    - master
+    # We want to build wip/* branches since these are not usually used for PRs
+    - /^wip\/.*$/
+    # We want to build version tags as well.
+    - /^v\d+\.\d+.*$/
+
+test_script:
   - "tox -e %TOX_PY%"