Lint messages link to docs for 0.0.212 which does not include all available lints

[phansch]

Currently, when installing Clippy on stable via Rustup, the links to the documentation in the lint output point to the documentation of 0.0.212.
That documentation does not include all the lints which are available in the distributed Clippy version.

So, when a newly added lint is triggered, opening the documentation link will not show the new lint, because it wasn't included in 0.0.212.

I can think of two solutions:

1. Update the version of the clippy_lints crate before the rustc submodule is updated.
2. Use the short commit hash in the link, instead of the version.

[matthiaskrgr]

Maybe we should use git describe to obtain version information via build.rs ?

[oli-obk]

We don't have per-commit docs yet. So we'd need to start creating those first. But we'd run into chicken/egg problems then (current code has no commit hash yet, but we need to have that in order to produce the commit). Also obtaining this info while in the rust build system is not possible.

I think the cleanest way would be to use the rustc major+minor version and have a cronjob on this repo that creates the appropriate pages whenever the beta compiler on travis is updated. If we only use the major+minor version, we don't need to update anything when the beta becomes stable (which shouldn't affect clippy at all anyway, at least not the docs).