non_exhaustive requires Rust 1.40.

224: Cleanup CI config r=taiki-e a=taiki-e

* FIx minimal versions check.
* Reduce CI time.


Co-authored-by: Taiki Endo <[email protected]>

This reverts commit 1bc75fd.

202: Allow naming the projected types r=taiki-e a=taiki-e

By passing an argument with the same name as the method to the attribute, you can name the projection type returned from the method:

```rust
#[pin_project(
    Replace,
    project = StructProj,
    project_ref = StructProjRef,
    project_replace = StructProjOwn,
)]
struct Struct<T> {
    #[pin]
    field: T,
}

let mut x = Struct { field: 0 };
let StructProj { field } = Pin::new(&mut x).project();
let StructProjRef { field } = Pin::new(&x).project_ref();
let StructProjOwn { field } = Pin::new(&mut x).project_replace(Struct { field: 1 });
```

cc #43
Closes #124

TODO: 
  * [x] add tests
  * [x] write docs 
  * [x] separate unrelated changes; done in #214
  * [x] msrv (`unrestricted_attribute_tokens` requires 1.34); done in #219 


Co-authored-by: Taiki Endo <[email protected]>