### What it does
Checks for use of File::read_to_end and File::read_to_string.

### Why is this bad?
`fs::{read, read_to_string}` provide the same functionality when `buf` is empty with fewer imports and no intermediate values.
See also: [fs::read docs](https://doc.rust-lang.org/std/fs/fn.read.html), [fs::read_to_string docs](https://doc.rust-lang.org/std/fs/fn.read_to_string.html)

### Example
```
let mut f = File::open("foo.txt").unwrap();
let mut bytes = Vec::new();
f.read_to_end(&mut bytes).unwrap();
```
Can be written more concisely as
```
let mut bytes = fs::read("foo.txt").unwrap();
```