Remove some more reads

[jgm]

Replace with safeRead.

• src/Text/Pandoc/Readers/TikiWiki.hs 505: return $B.str [toEnum (read inner :: Int) :: Char]

• src/Text/Pandoc/Writers/Docx.hs 237: let pgContentWidth = (-) <$> (read <$> mbAttrSzWidth ::Maybe Integer) 239: (+) <$> (read <$> mbAttrMarRight ::Maybe Integer) 240: <*> (read <$> mbAttrMarLeft ::Maybe Integer)

• src/Text/Pandoc/Writers/LaTeX.hs 558: '%':ds -> showFl (read (reverse ds) / 100 :: Double)