Add mathtools package to LaTeX template

Author: peterbjohnson

src/template.latex

@@ -9,7 +9,7 @@ $if(linestretch)$
 \setstretch{$linestretch$}
 $endif$
 \usepackage{braket,cancel}
-\usepackage{amssymb,amsmath}
+\usepackage{amssymb,amsmath,mathtools}
 \usepackage{ifxetex,ifluatex}
 \usepackage{fixltx2e} % provides \textsubscript
 \ifnum 0\ifxetex 1\fi\ifluatex 1\fi=0 % if pdftex