Only select  parts from manifest that are also in spine

Partially resolves #34
TODO: use the order of the spine elements
diff --git a/xslt/epub2i5.xsl b/xslt/epub2i5.xsl
index 4659dc4..32243e6 100644
--- a/xslt/epub2i5.xsl
+++ b/xslt/epub2i5.xsl
@@ -404,7 +404,7 @@
                    <body>
                     <!-- Call the template for each link in the TOC 
                          <xsl:apply-templates select="//xhtml:ol[@class='toc']/xhtml:li/xhtml:a" mode="collect"/> -->
-                    <xsl:apply-templates select="//opf:package/opf:manifest/opf:item[matches(@href, '\.x?html?$') and not(matches(@href, '(cover|toc|copyright|feedback|inhalt|nav|titlepage).*'))]" mode="collect"/>
+                    <xsl:apply-templates select="//opf:package/opf:manifest/opf:item[exists(//spine/itemref/@idref=@id) and matches(@href, '\.x?html?$') and not(matches(@href, '(cover|toc|copyright|feedback|inhalt|nav|titlepage).*'))]" mode="collect"/>
                     </body>
                 </text>
             </idsText>