0.6.0: improve `Entry` and added `Archive::download()`

• b9dc171 test: added some negative test for download
• 42819a8 ci: added builds/tests for the download feature
• 2344619 doc: added more info in README.md
• e5a973d feat: added the option to download an archive from a URL
• f093f21 refactor: allow for archive to be stored in temp directory
• 1236614 feat: added Archive::entry_by_name()
• e9647cc feat: added Archive::format() and Archive::path()
• d7c2f5c fix: allow the functions on Archive to be called multiple times
• 2733a29 refactor: Archive has named fields.
• 7609046 feat: added is_dir(), is_file() to Entry struct
• 8daa73a feat: added size() method to the Entry struct.
• 2ad1633 chore: prepare for next release