Use official component availability page
Now that rustup-components-history is accepted[1] to the offical repository,
it makes sense to link to it directly from rustup.rs front page.
[1]:
<br/>
<a href="https://github.com/rust-lang/rustup.rs/#other-installation-methods">other installation options</a>
&nbsp;&middot;&nbsp;
- <a href="https://rust-lang-nursery.github.io/rust-toolstate/">component availability</a>
+ <a href="https://rust-lang.github.io/rustup-components-history/">component availability</a>
&nbsp;&middot;&nbsp;
<a href="https://github.com/rust-lang/rustup.rs">about rustup</a>
</p>
