lints!

[seanmonstar]

Specifically, this will prevent 2 code smells:

1. glob: use foo::* is by default denied. use self::sub::* is fine, as way to uplift sub modules. For uses of bad globs, they must be covered with a #[glob = "explanation"] attribute.
2. str_to_string: Micro benchmarks show it's 5x slower than &str.into_string(). So this lint denies such usage.

[seanmonstar]

oh dangit, i forgot to feature gate the attributes

[reem]

I think it might be best to move these lints into other repos/crates, since they are actually generally useful (I'd like to use them in other projects, especially str_to_string) and it keeps the codebase of hyper itself short.

We could have a hyper/lints or you could just stick them in your own repo.

[Manishearth]

The tostring lint has been upstreamed into Clippy. I think the glob one would be nice to have as well, PRs welcome! :)