update example to use CodeBuilder

Author: niklasf

src/lib.rs

@@ -18,9 +18,10 @@
 //! # use std::error::Error;
 //! #
 //! # fn try_main() -> Result<(), Box<Error>> {
+//! use std::iter::FromIterator;
 //! use std::collections::HashMap;
 //! use bit_vec::BitVec;
-//! use huffman_compress::{Book, Tree, codebook};
+//! use huffman_compress::{CodeBuilder, Book, Tree};
 //!
 //! let mut weights = HashMap::new();
 //! weights.insert("CG", 293);
@@ -31,7 +32,7 @@
 //!
 //! // Construct a Huffman code based on the weights (e.g. counts or relative
 //! // frequencies).
-//! let (book, tree) = codebook(&weights);
+//! let (book, tree) = CodeBuilder::from_iter(weights).finish();
 //!
 //! // More frequent symbols will be encoded with fewer bits.
 //! assert!(book.get("CG").map_or(0, |cg| cg.len()) <