Added improve ordinal position

This partially addresses issue #14.

Sources/Introduction.tex

@@ -135,7 +135,11 @@ These should be added in equal measure to your own conduct. To typeset
 units correctly, use the \verb|siunitx| package. For example, you might
 want to restrict your daily intake of liberty to \SI{750}{\milli\gram}.
 
-Likewise, as a small pet peeve of mine, I offer specific operators for \emph{ordinals}. Use \verb|\th| to typeset things like July~4\th correctly. Or, if you are referring to the 2\nd edition of a book, please use \verb|\nd|. Likewise, if you came in 3\rd in a marathon, use \verb|\rd|. This is my 1\st rule.
+Likewise, as a small pet peeve of mine, I offer specific operators for
+\emph{ordinals}. Use \verb|\th| to typeset things like July~4\th
+correctly. Or, if you are referring to the 2\nd edition of a book,
+please use \verb|\nd|. Likewise, if you came in 3\rd in a marathon, use
+\verb|\rd|. This is my 1\st rule.
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{Changing things}

mimosis.cls

@@ -203,10 +203,17 @@
 % Ordinals
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-\newcommand  {\st}{\textsuperscript{\textup{st}}\xspace}
-\newcommand  {\rd}{\textsuperscript{\textup{rd}}\xspace}
-\newcommand  {\nd}{\textsuperscript{\textup{nd}}\xspace}
-\renewcommand{\th}{\textsuperscript{\textup{th}}\xspace}
+\ifxetexorluatex
+  \newcommand  {\st}{{\addfontfeatures{VerticalPosition=Ordinal}\textup{st}}\xspace}
+  \newcommand  {\rd}{{\addfontfeatures{VerticalPosition=Ordinal}\textup{rd}}\xspace}
+  \newcommand  {\nd}{{\addfontfeatures{VerticalPosition=Ordinal}\textup{nd}}\xspace}
+  \renewcommand{\th}{{\addfontfeatures{VerticalPosition=Ordinal}\textup{th}}\xspace}
+\else
+  \newcommand  {\st}{\textsuperscript{\textup{st}}\xspace}
+  \newcommand  {\rd}{\textsuperscript{\textup{rd}}\xspace}
+  \newcommand  {\nd}{\textsuperscript{\textup{nd}}\xspace}
+  \renewcommand{\th}{\textsuperscript{\textup{th}}\xspace}
+\fi
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % Penalties