\documentclass{article}
\usepackage{modular}
\usepackage[pdfpagemode=UseNone,pdfstartview=FitH,colorlinks=true,linkcolor=blue,citecolor=blue,urlcolor=blue]{hyperref}
\usepackage{listings}
\lstset{language=[LaTeX]TeX, linewidth=0.9\textwidth, frame=single}

\newcommand{\coseoul}{\texttt{coseoul}}
\newcommand{\fixedwidth}[1]{\texttt{#1}}
\newcommand{\levelstaytext}{\texttt{\backslash levelstay}}

\title{Modular LaTeX Documents: \textbf{modular}}
\author{Daniel Thomas Sank}
\date{2016 December 27}

\begin{document}

\maketitle
\tableofcontents

% \subimport* comes from the `import` package.
\subimport*{./}{content.tex}

\end{document}