ulate increased indentation level. Will not really work
-- for multi-line paragraphs.
indent :: Block -> Block
indent = indentBlock
  where
  -- indentation space
  spacer :: String
  spacer = replicate 4 ' '
  --
  indentBlock (Plain ins) = Plain ((Str spacer):ins)
  indentBlock (Para ins) = Para ((Str spacer):ins)
  indentBlock (CodeBlock a s) =
    let s' = unlines . map (spacer++) . lines $ s
    in  CodeBlock a s'
  indentBlock (BlockQuote bs) = BlockQuote (map indent bs)
  indentBlock (Header l attr' ins) = Header l attr' (indentLines ins)
  indentBlock everythingElse = everythingElse
  -- indent every (explicit) line
  indentLines :: [Inline] -> [Inline]
  indentLines ins = let lns = split isLineBreak ins :: [[Inline]]
                    in  intercalate [LineBreak] $ map ((Str spacer):) lns

capit
indent :: Block -> Block
indent = indentBlock
  where
  -- indentation space
  spacer :: String
  spacer = replicate 4 ' '
  --
  indentBlock (Plain ins) = Plain ((Str spacer):ins)
  indentBlock (Para ins) = Para ((Str spacer):ins)
  indentBlock (CodeBlock a s) =
    let s' = unlines . map (spacer++) . lines $ s
    in  CodeBlock a s'
  indentBlock (BlockQuote bs) = BlockQuote (map indent bs)
  indentBlock (Header l attr' ins) = Header l attr' (indentLines ins)
  indentBlock everythingElse = everythingElse
  -- indent every (explicit) line
  indentLines :: [Inline] -> [Inline]
  indentLines ins = let lns = split isLineBreak ins :: [[Inline]]
                    in  intercalate [LineBreak] $ map ((Str spacer):) lns
indent = indentBlock
  where
  -- indentation space
  spacer :: String
  spacer = replicate 4 ' '
  --
  indentBlock (Plain ins) = Plain ((Str spacer):ins)
  indentBlock (Para ins) = Para ((Str spacer):ins)
  indentBlock (CodeBlock a s) =
    let s' = unlines . map (spacer++) . lines $ s
    in  CodeBlock a s'
  indentBlock (BlockQuote bs) = BlockQuote (map indent bs)
  indentBlock (Header l attr' ins) = Header l attr' (indentLines ins)
  indentBlock everythingElse = everythingElse
  -- indent every (explicit) line
  indentLines :: [Inline] -> [Inline]
  indentLines ins = let lns = split isLineBreak ins :: [[Inline]]
                    in  intercalate [LineBreak] $ map ((Str spacer):) lns