Start trying to get Windows CI working, refs #511

.travis.yml

@@ -2,15 +2,27 @@ language: python
 dist: xenial
 
 # 3.6 is listed first so it gets used for the later build stages
-python:
-  - "3.6"
-  - "3.7"
-  - "3.5"
+matrix:
+  include:
+    - os: linux
+      python: "3.6"
+    - os: linux
+      python: "3.5"
+    - os: linux
+      python: "3.7"
+    - os: windows
+      language: bash
+      name: Windows
+
+install:
+    - if [ "$TRAVIS_OS_NAME" = "windows" ]; then
+      choco install python3;
+
 
 # Executed for 3.5 AND 3.5 as the first "test" stage:
 script:
-  - pip install -U pip wheel
-  - pip install .[test]
+  - python -m pip install -U pip wheel
+  - python -m pip install .[test]
   - pytest
 
 cache:
@@ -23,7 +35,7 @@ jobs:
     - stage: deploy latest.datasette.io
       if: branch = master AND type = push
       script:
-        - pip install .[test]
+        - python -m pip install .[test]
         - npm install -g now
         - python tests/fixtures.py fixtures.db fixtures.json
         - export ALIAS=`echo $TRAVIS_COMMIT | cut -c 1-7`