run CI on Windows using AppVeyor

.appveyor.yml

@@ -0,0 +1,21 @@
+version: "{build}"
+clone_depth: 1
+clone_folder: c:\gopath\src\github.com\rhysd\go-github-selfupdate
+environment:
+    GOPATH: c:\gopath
+install:
+    - echo %PATH%
+    - echo %GOPATH%
+    - go version
+    - go env
+    - go get -v -t -d ./...
+build: off
+test_script:
+    - go build ./selfupdate
+    - go build ./cmd/selfupdate-example
+    - go test -v -race -coverprofile=coverage.txt ./selfupdate
+after_test:
+    - "SET PATH=C:\\Python34;C:\\Python34\\Scripts;%PATH%"
+    - pip install codecov
+    - codecov -f "coverage.txt"
+deploy: off