clean up example

//!

//! fn main() {

//!     let rsa = Rsa::generate(2048).unwrap();

//!     let data: Vec<u8> = String::from("foobar").into_bytes();

//!     let mut encrypted_data: Vec<u8>  = vec![0; 512];

//!     let padding = Padding::PKCS1;

//!     let _ = rsa.public_encrypt(&data, encrypted_data.as_mut_slice(), padding).unwrap();

//!     let data = b"foobar";

//!     let mut buf = vec![0; rsa.size() as usize];

//!     let encrypted_len = rsa.public_encrypt(data, &mut buf, Padding::PKCS1).unwrap();

//! }

//! ```

use ffi;