Expose functionality for creating core types (#578)

* You can now add chapters to a Book

* Made the RenderContext::new() constructor public

src/book/book.rs

@@ -101,6 +101,12 @@ impl Book {
     {
         for_each_mut(&mut func, &mut self.sections);
     }
+
+    /// Append a `BookItem` to the `Book`.
+    pub fn push_item<I: Into<BookItem>>(&mut self, item: I) -> &mut Self {
+        self.sections.push(item.into());
+        self
+    }
 }
 
 pub fn for_each_mut<'a, F, I>(func: &mut F, items: I)
@@ -126,6 +132,12 @@ pub enum BookItem {
     Separator,
 }
 
+impl From<Chapter> for BookItem {
+    fn from(other: Chapter) -> BookItem {
+        BookItem::Chapter(other)
+    }
+}
+
 /// The representation of a "chapter", usually mapping to a single file on
 /// disk however it may contain multiple sub-chapters.
 #[derive(Debug, Clone, Default, PartialEq, Serialize, Deserialize)]

src/renderer/mod.rs

@@ -26,6 +26,8 @@ use errors::*;
 use config::Config;
 use book::Book;
 
+const MDBOOK_VERSION: &str = env!("CARGO_PKG_VERSION");
+
 /// An arbitrary `mdbook` backend.
 ///
 /// Although it's quite possible for you to import `mdbook` as a library and
@@ -68,7 +70,7 @@ pub struct RenderContext {
 
 impl RenderContext {
     /// Create a new `RenderContext`.
-    pub(crate) fn new<P, Q>(root: P, book: Book, config: Config, destination: Q) -> RenderContext
+    pub fn new<P, Q>(root: P, book: Book, config: Config, destination: Q) -> RenderContext
     where
         P: Into<PathBuf>,
         Q: Into<PathBuf>,
@@ -76,7 +78,7 @@ impl RenderContext {
         RenderContext {
             book: book,
             config: config,
-            version: env!("CARGO_PKG_VERSION").to_string(),
+            version: MDBOOK_VERSION.to_string(),
             root: root.into(),
             destination: destination.into(),
         }