Allow quoting of multiple posts in a range

[emmiegit]

Sometimes people spread their ideas across multiple messages.
.quote should be changed to allow these multiple messages to be merged into one embed for quoting purposes.

The new usage could be .quote start-message-id [end-message-id], and would fail if that range spanned over posts by more than one author.

[emmiegit]

Actually, we could have it collect all messages by the same author into the same embed, and create a new one for the next user. This would allow quoting of conversations or back-and-forth exchanges.

[emmiegit]

New usage: .quote start-message-id [end-message-id or 0] [channel-id]