Switch to github.com/google/uuid dependency.

It seems to be more well maintained and reliable at this time.

google/uuid works out of box with Go modules, because the most recently
tagged version is compatible with master (at this time, they're equal).
On the other hand, using satori/go.uuid requires reverting back to an
older API because its latest tag is more significantly behind master.
See satori/go.uuid#90, satori/go.uuid#82, satori/go.uuid#76.

usercontent.go

@@ -7,7 +7,7 @@ import (
 	"os"
 	pathpkg "path"
 
-	"github.com/satori/go.uuid"
+	"github.com/google/uuid"
 	"github.com/shurcooL/httperror"
 	"github.com/shurcooL/users"
 	"github.com/shurcooL/webdavfs/vfsutil"
@@ -47,7 +47,7 @@ func (uc userContentHandler) Upload(w http.ResponseWriter, req *http.Request) er
 		return httperror.JSONResponse{V: uploadResponse{Error: err.Error()}}
 	}
 
-	uuid, err := uuid.NewV4()
+	uuid, err := uuid.NewRandom()
 	if err != nil {
 		return httperror.JSONResponse{V: uploadResponse{Error: err.Error()}}
 	}