Changed misleading documentation on markdown2pdf.

markdown2pdf used to create a backup file if the output file
exists; it doesn't any longer, but the documentation still said
it does.

README

@@ -102,8 +102,7 @@ for example,
 
     markdown2pdf sample.txt endnotes.txt
 
-will produce `sample.pdf`.  (If `sample.pdf` exists already,
-it will be backed up before being overwritten.)  An output file
+will produce `sample.pdf`.  An output file
 name can be specified explicitly using the `-o` option:
 
     markdown2pdf -o book.pdf chap1 chap2

src/markdown2pdf.hs

@@ -257,7 +257,7 @@ main = withTempDir "pandoc"
         case latexRes of
           Left err      -> exit err
           Right pdfFile -> do
-            -- save the output creating a backup if necessary
+            -- save the output
             saveOutput pdfFile $
               replaceDirectory pdfFile (takeDirectory output)