Updated rustwide to 0.7.1

[Kixiron]

As discussed on discord, this is part of an attempt to semi-incrementally re-implement step 1 of the async RFC now that the (hopefully) root cause of the crash was solved with git gc

[jyn514]

Some more things mentioned:

• This means we will depend on both tokio 0.1 and 0.2, but since we plan to follow it up shortly with the rest of Update asynchronous dependencies #758, that seems reasonable.
• Since Rustwide uses tokio much less heavily, it is unlikely this will have a performance impact (or at least, not nearly as bad as Update asynchronous dependencies #758)