LaTeX writer: Fixed spacing in quote environments.

Closes #502.  Previously you'd get:

~~~
hi

\begin{quote}
hi

\end{quote}
hi
~~~

Now we get:

~~~
hi

\begin{quote}
hi
\end{quote}

hi
~~~

src/Text/Pandoc/Writers/LaTeX.hs

@@ -278,7 +278,8 @@ blockToLaTeX (BlockQuote lst) = do
          return result
        _ -> do
          contents <- blockListToLaTeX lst
-         return $ "\\begin{quote}" $$ contents $$ "\\end{quote}"
+         return $ "\\begin{quote}" $$ chomp contents $$ "\\end{quote}"
+                  <> blankline
 blockToLaTeX (CodeBlock (_,classes,keyvalAttr) str) = do
   opts <- gets stOptions
   case () of

tests/lhs-test.latex

@@ -86,7 +86,6 @@ Block quote:
 
 \begin{quote}
 foo bar
-
 \end{quote}
 
 \end{document}

tests/lhs-test.latex+lhs

@@ -66,7 +66,6 @@ Block quote:
 
 \begin{quote}
 foo bar
-
 \end{quote}
 
 \end{document}

tests/writer.latex

@@ -119,8 +119,8 @@ E-mail style:
 
 \begin{quote}
 This is a block quote. It is pretty short.
-
 \end{quote}
+
 \begin{quote}
 Code in a block quote:
 
@@ -141,13 +141,13 @@ Nested block quotes:
 
 \begin{quote}
 nested
-
 \end{quote}
+
 \begin{quote}
 nested
+\end{quote}
+\end{quote}
 
-\end{quote}
-\end{quote}
 This should not be a block quote: 2 \textgreater{} 1.
 
 And a following paragraph.
@@ -476,8 +476,8 @@ orange fruit
 \end{verbatim}
 \begin{quote}
 orange block quote
-
 \end{quote}
+
 \end{description}
 Multiple definitions, tight:
 
@@ -809,8 +809,8 @@ An e-mail address:
 
 \begin{quote}
 Blockquoted: \url{http://example.com/}
-
 \end{quote}
+
 Auto-links should not occur here:
 \texttt{\textless{}http://example.com/\textgreater{}}
 
@@ -855,8 +855,8 @@ note.\footnote{This is \emph{easier} to type. Inline notes may contain
 
 \begin{quote}
 Notes can go in quotes.\footnote{In quote.}
-
 \end{quote}
+
 \begin{enumerate}[1.]
 \item
   And in list items.\footnote{In list.}