Appveyor support (#2)

.appveyor/install.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+
+export PATH="/mingw64/bin:${PATH}"
+export PKG_CONFIG_PATH="/mingw64/lib/pkgconfig:${PKG_CONFIG_PATH}"
+export GOROOT=/mingw64/lib/go
+export GOPATH=/go
+export CGO_ENABLED=1
+
+pacman --noconfirm -S \
+    mingw64/mingw-w64-x86_64-go \
+    mingw64/mingw-w64-x86_64-libusb
+
+go version
+go get -t github.com/google/gousb/...
+go test github.com/google/gousb/...