Update to acmart 2.0

[dragonstyle]

Part 1 of fix to #34
Also fixes #19

[dragonstyle]

This update appears to be properly using the latest version (which I think is a good idea since CTAN is distributing this version). I did try using the old 'cls' file for simplicity, but other packages (hyperxmp specifically) have updated in ways that broke that version, so sticking with the old version seems a bad idea.

@cscheid Would love your review. Also note that currently when I attempt to render to acm-pdf I think there are tweaks to fancy-figure.lua required - it is currently failing due to our buddy par mode. I'll try to dig into this and fix but if you happen to see his and know what is going on, feel free to party on this branch.

(ending up with this tex:

\begin{figure}

\centering{

\begin{figure}
{\centering \includegraphics{sample-franklin.png}}
\caption{}
\Description{A woman and a girl in white dresses sit in an open car.}
\end{figure}

}

\caption{\label{fig-dresses}1907 Franklin Model D roadster. Photograph
by Harris \& Ewing, Inc.~{[}Public domain{]}, via Wikimedia Commons.
(\url{https://goo.gl/VLCRBB}).}

\end{figure}%