fix the plm convergence plot -- wrong limiters were used

closes issue #2

Author: zingale

advection/advection.tex

@@ -837,6 +837,21 @@ \section{Errors and convergence rate}
         \hydroexdoit{\href{https://github.com/zingale/hydro_examples/blob/master/advection/advection.py}{advection.py}}}
 \end{figure}
 
+\begin{figure}[ht]
+\centering
+\includegraphics[width=0.8\linewidth]{fv-gaussian-limiters} \\[1em]
+\includegraphics[width=0.8\linewidth]{fv-tophat-limiters} 
+\caption[Effect of different limiters on evolution]
+        {\label{fig:limiter_panel} The effect of different limiters on the
+          evolution of a Gaussian initial profile (top) and a tophat initial
+          profile (bottom), using $C = 0.8$ and 5 periods. \\
+        \hydroexdoit{\href{https://github.com/zingale/hydro_examples/blob/master/advection/advection.py}{advection.py}}}
+\end{figure}
+
+As seen in figure~\ref{fig:advnorm}, the choice of limiters can have a great
+effect on the accuracy.  Figure~\ref{fig:limiter_panel} shows the Gaussian and
+tophat profiles with several different limiters.
+
 \section{Multi-dimensional advection}
 
 The two-dimensional linear advection equation is:

advection/fv-gaussian-limiters.pdf

@@ -202,7 +202,7 @@ \section{Burgers' equation}
 
 \begin{exercise}[Simple Burgers' solver]
 {Extend your 1-d finite-volume solver for advection (from
-  Exercise~\ref{adv:ex:fv}) to solver Burgers' equation.  You will
+  Exercise~\ref{adv:ex:fv}) to solve Burgers' equation.  You will
   need to change the Riemann solver and use the local velocity in the
   construction of the interface states.  Run the examples shown in
   Figures~\ref{fig:burgers-rarefaction} and \ref{fig:burgers-shock}}.