Rustup to rustc 1.30.0-nightly (6bf6d50a6 2018-08-19)

[Manishearth]

rust-lang/rust#52953

[Manishearth]

Removed branch protection rule for the rustup branch -- why do we need it?

[oli-obk]

I once thought that we'd have master which builds on nightly and rustup which builds on rustc-master. This way contributers could develop on master and we'd keep merging the two branches into each other whenever convenient

[Manishearth]

Hmmm. That works, but requires even more coordination -- perhaps we can request contributors to use rustc-master?

[oli-obk]

If we get that to work for travis, then sure