Add usernames from expansions to columns

[igorbrigadir]

Currently there are user IDs only, but it would help to also have user names. Not all user columns should be added, as this would make an unreasonably wide dataframe (would need all author columns for each quoted, retweeted, etc user) but just adding names is enough to make things easier.

Additionally, document extracting and converting user objects too maybe.

[igorbrigadir]

On second look this is significantly more awkward - but might still be possible.

[igorbrigadir]

I went with a simpler approach, just usernames there are now extra columns:

in_reply_to_username
retweeted_username
quoted_username

Which should cover all the possibilities (A tweet can be both a reply and a quote for example)