Make sky_server include no-cache headers since we don't really want caching during development.

sky/tools/skygo/sky_server.go

Index: sky/tools/skygo/sky_server.go
diff --git a/sky/tools/skygo/sky_server.go b/sky/tools/skygo/sky_server.go
index a8ca2ccc9bbac3d50fc3218bb3a4744175ab302c..482e6694a2712bad90d58bb6a3a64d9794eeb40b 100644
--- a/sky/tools/skygo/sky_server.go
+++ b/sky/tools/skygo/sky_server.go
@@ -28,6 +28,7 @@ func (handler *skyHandlerRoot) ServeHTTP(w http.ResponseWriter, r *http.Request)
     if strings.HasSuffix(path, ".sky") {
         w.Header().Set("Content-Type", "text/sky")
     }
+    w.Header().Set("Cache-Control", "no-cache")
     http.ServeFile(w, r, path)
 }