Package rename in vendored dependencies

[nicktrav]

Hello! We're working on integrating Veneur into our (mono)repo, and are running up against some vendoring issues.

Specifically, x/net/http in this repo is older than the one we're using, which contains some package renames (namely lex/httplex moved into http/httpguts).

Here's the specific change: golang/net@cbb82b5

I've bumped the version locally to the latest upstream, and everything looks good, so I'd be more than happy to offer that up as a patch.

Thanks!