Remove centering for floats (#364)

This was a bad idea...:
https://tex.stackexchange.com/questions/2651/should-i-use-center-or-centering-for-figures-and-tables

floatrows not sure how it should work with flowcharts... so we use
centring

I don't want to redefine all floats either as we use them for chapters
title page.

book/troubleshooting/misc.tex

@@ -188,12 +188,11 @@ protecting your sourdough starter from aerobic mold entering through
 the top.
 
 \begin{figure}[!htb]
-\begin{center}
+\centering
   \includegraphics[width=0.5\textwidth]{sourdough-starter-hooch}
   \caption[Hooch] {Hooch building on top of a sourdough
       starter~\cite{liquid+on+starter}.}%
   \label{fig:hooch}
-\end{center}
 \end{figure}
 
 Simply stir your sourdough starter to homogenize the hooch back
@@ -321,12 +320,11 @@ When tasting acetic acid, the flavor of your bread is often perceived
 as quite strong.
 
 \begin{figure}[!htb]
-\begin{center}
+\centering
   \input{figures/fig-ethanol-oxidation.tex}
   \caption[Acetic acid creation]{Oxygen is required to create acetic
       acid~\cite{acetic+acid+production}.}%
   \label{fig:ethanol-oxidation}
-\end{center}
 \end{figure}
 
 This is nothing bad. But if you would like to change