vendor: update all dependencies except Azure SDK

The Azure SDK doesn't support Go 1.5 anymore. We can't upgrade it until
Go 1.8 comes out.

vendor/golang.org/x/tools/imports/fix.go

@@ -462,6 +462,9 @@ func shouldTraverse(dir string, fi os.FileInfo) bool {
 	if !ts.IsDir() {
 		return false
 	}
+	if skipDir(ts) {
+		return false
+	}
 
 	realParent, err := filepath.EvalSymlinks(dir)
 	if err != nil {