Adds Book parser

src/fetch.cr

@@ -2,11 +2,17 @@ require "crest"
 
 module Muse::Dl
   class Fetch
-    def get_info(url : String) : (Muse::Dl::Book | Muse::Dl::Issue)
+    def get_info(url : String) : (Muse::Dl::Book | Muse::Dl::Journal)
       match = /https:\/\/muse.jhu.edu\/(book|journal)\/(\d+)/.match url
       if match
         begin
           response = Crest.get url
+          case match[1]
+          when "book"
+            return Muse::Dl::Book.new response
+          when "journal"
+            return Muse::Dl::Journal.new response
+          end
         rescue ex : Crest::NotFound
           raise Muse::Dl::InvalidLink
         end

src/muse-dl.cr

@@ -1,6 +1,7 @@
 require "./parser.cr"
 require "./pdftk.cr"
 require "./fetch.cr"
+require "./book.cr"
 
 # TODO: Write documentation for `Muse::Dl`
 module Muse::Dl