Update bytes to 0.6.

[najamelan]

This allows dependent crates to use the latest version of bytes.

[mxinden]

@matthunz friendly ping. What do you think of bumping bytes?

[mxinden]

I will try once more. @matthunz would you mind taking a look at this pull request? This is blocking all downstream crates to update. Please let me know in case I can be of any help.

[pimeys]

This should now go to bytes 1.0, and it would be great if we'd get a new version soon. :)

[Keruspe]

@matthunz do you need help for getting a released with bytes 1.0?

[mxinden]

futures-codec not updating to bytes v1.0 blocked many downstream crates e.g. rust-libp2p to upgrade other dependencies. I decided to fork futures-codec to provide a fully upgraded version: https://github.com/mxinden/asynchronous-codec

For now asynchronous-codec is a 1-to-1 fork of futures-codec, differing only in its dependency versions. In the future I plan to incorporate improvements like #54 while keeping dependencies up to date via Dependabot.

@matthunz I am happy to collaborate on merging the two projects (futures-codec and asynchronous-codec) again. This likely goes without saying: I forked futures-codec out of necessity, not out of bad faith. I preserved the git history and license. In addition you are mentioned as the original author in the readme. Thanks for open sourcing futures-codec.