Get the filesystem path of a file.
A simple extension trait for `File` that provides a single method `path`, which returns the path of a file.
**Note**: Not every file has a path. The path might be wrong for example after moving a file.
OS support: Linux, Mac, Windows
```rust
use std::fs::File;
use filepath::FilePath;
let mut file = File::create("foo.txt").unwrap();
println!("{:?}", file.path());
```