Add multi-line support to `print_header` in youtube_download.py
Simplify `read_data_at_url` in youtube_download.py
Minor consistency change to `SEARCH_SIGNATURE_EQUALS_RE` in youtube_download.py
Add check to `get_download_links` in youtube_download.py
Return `title` from `get_download_links` in youtube_download.py
Add `get_playlist_links` to youtube_download.py
Add `output_directory` argument to `main` in youtube_download.py