Documentation for read_mode option

[brucepom]

Hi there, thanks for the great package.

It seems like outdated reads can be permitted like so:
table("table_name", read_mode: :outdated)

The docs here still talk about the useOutdated option though.
https://hexdocs.pm/rethinkdb/RethinkDB.Query.html#table/1 !

I can submit a pull request for the change if it's helpful. It looks like the options passed to table are relayed directly to RethinkDB. So maybe instead we could add a note suggesting consulting the RethinkDB docs for your version of RethinkDB?

Thanks again

[hamiltop]

Any doc updates would be greatly appreciated! Thanks!