remove unused imports

src/book/bookconfig.rs

@@ -1,5 +1,4 @@
 use serde_json;
-use serde_json::Value;
 use std::fs::File;
 use std::io::Read;
 use std::path::{Path, PathBuf};

src/book/bookitem.rs

@@ -1,6 +1,5 @@
 use serde::{Serialize, Serializer};
 use std::path::PathBuf;
-use std::collections::BTreeMap;
 
 #[derive(Debug, Clone)]
 pub enum BookItem {

src/renderer/html_handlebars/hbs_renderer.rs

@@ -12,7 +12,6 @@ use std::collections::BTreeMap;
 
 use handlebars::Handlebars;
 
-use serde::Serialize;
 use serde_json;
 use serde_json::value::ToJson;