Fixed underlining of \emph in PDF.

Thought I had this fixed, not sure why it came back. Had to add
\normalem to template file to force \emph to be italics, which is
the default. Not sure why it has been doing underlining recently.

pdf/book.tplx

@@ -11,6 +11,7 @@
 ((* endblock docclass *))
  
 ((* block preamble *))
+
 ((* endblock preamble *))
  
 ((* block title *))
@@ -19,6 +20,7 @@
 ((* endblock title *))
 
 ((* block markdowncell scoped *))
+\normalem
 \setlength{\parindent}{0em}
 \setlength{\parskip}{0.5em}
     ((( cell.source | citation2latex | strip_files_prefix | markdown2latex(extra_args=["--chapters"]) )))