优化epublib,清除警告，尝试兼容epub v3格式的导出。

app/src/main/java/io/legado/app/model/localBook/EpubFile.kt

@@ -120,7 +120,7 @@ class EpubFile(var book: Book) {
                 }
                 resources.add(resource)
             } while (zipEntry != null)
-            if (resources.size() > 0) return EpubReader().readEpub(resources)
+            if (resources.size() > 0) return EpubReader().readEpubBook(resources)
         } catch (e: Exception) {
             e.printStackTrace()
         }

epublib/src/main/java/me/ag2s/epublib/domain/EpubBook.java

@@ -5,4 +5,5 @@ package me.ag2s.epublib.domain;
  */
 @SuppressWarnings("unused declaration")
 public class EpubBook extends Book {
+
 }

epublib/src/main/java/me/ag2s/epublib/epub/EpubReader.java

@@ -14,6 +14,7 @@ import java.util.zip.ZipInputStream;
 
 import me.ag2s.epublib.Constants;
 import me.ag2s.epublib.domain.Book;
+import me.ag2s.epublib.domain.EpubBook;
 import me.ag2s.epublib.domain.MediaType;
 import me.ag2s.epublib.domain.MediaTypes;
 import me.ag2s.epublib.domain.Resource;
@@ -30,7 +31,7 @@ public class EpubReader {
 
     private static final String TAG = EpubReader.class.getName();
     private final BookProcessor bookProcessor = BookProcessor.IDENTITY_BOOKPROCESSOR;
-
+    @SuppressWarnings("unused")
     public Book readEpub(InputStream in) throws IOException {
         return readEpub(in, Constants.CHARACTER_ENCODING);
     }
@@ -97,9 +98,13 @@ public class EpubReader {
         return readEpub(resources);
     }
 
+    @SuppressWarnings("unused")
     public Book readEpub(Resources resources) {
         return readEpub(resources, new Book());
     }
+    public EpubBook readEpubBook(Resources resources) {
+        return (EpubBook) readEpub(resources, new Book());
+    }
 
     public Book readEpub(Resources resources, Book result) {
         if (result == null) {