Update README.md

Fix typo
Fix inner attribute syntax from `#[foo];` to `#![foo]`

From the 0.10 changelog:
 * The inner attribute syntax has changed from `#[foo];` to `#![foo]`.
Add stdlib docs to the Linux binary tarball.

These are not installed anywhere, but are included under `./doc` for
those who want an offline copy with their nightlies. This increases the
size of the (compressed) tarball from 76 to 83 MB.
syntax: remove obsolete mutability from ExprVec and ExprRepeat.
std: TrieSet should implement container::{,Mutable}Set
extra: Add with_capacity to PriorityQueue and SmallIntMap
Register new snapshots
Added grow_fn and retain to Vec
rustc: Always name bytecode based on crate ids

When performing LTO, bytecode is loaded from an archive by using the crate id's
name. If the -o flag was specified when building the original library, it
previously also mangled the name of the bytecode.

This switches to always using the crate id's name when naming the bytecode file,
ensuring that it can always be loaded at a later date, regardless of -o.

Closes #13317
Test fixes from rollup
auto merge of #13326 : alexcrichton/rust/rollup, r=alexcrichton

Closes #13313 (Fix typo in README.md)
Closes #13311 (Fix inner attribute syntax from `#[foo];` to `#![foo]`)
Closes #13309 (Add stdlib docs to the Linux binary tarball.)
Closes #13308 (syntax: remove obsolete mutability from ExprVec and ExprRepeat.)
Closes #13306 (TrieSet should impl Set/MutableSet; add with_capacity to PriorityQueue/SmallIntMap)
Closes #13303 (Register new snapshots)
Closes #13274 (Added grow_fn and retain to Vec)

*Issues Closed*

Closes #13249