Dependency to a directory - parquet file

Some file formats like `parquet` create file directory with dozens of files instead of a single file. We should handle this scenario.

```
$ dvc run --input-file data/input.csv --output-dir data/output.pq mycode.py data/input.csv data/output.pq
$ ls data/output.pq
part-000001.pq@ part-000001.pq@ part-000003.pq@ summary
```