Org reader: allow trailing spaces after key/value pairs in directives

Ensures that spaces at the end of attribute directives like
`#+ATTR_HTML: :width 100%` (note the trailing spaces) are accepted.

src/Text/Pandoc/Readers/Org/Blocks.hs

@@ -167,9 +167,8 @@ keyValues = try $
    value = skipSpaces *> manyTillChar anyChar endOfValue
 
    endOfValue :: Monad m => OrgParser m ()
-   endOfValue =
-     lookAhead $ (() <$ try (many1 spaceChar <* key))
-              <|> () <$ newline
+   endOfValue = lookAhead (void $ try (many1 spaceChar <* key))
+            <|> try (skipSpaces <* lookAhead newline)
 
 
 --

test/Tests/Readers/Org/Inline.hs

@@ -213,6 +213,14 @@ tests =
                 ] =?>
       para (imageWith ("", [], [("width", "50%")]) "guinea-pig.gif" "" "")
 
+    , "HTML attributes can have trailing spaces" =:
+      T.unlines [ "#+attr_html: :width 100% :height 360px  "
+                , "[[file:fireworks.jpg]]"
+                ] =?>
+      let kv = [("width", "100%"), ("height", "360px")]
+      in para (imageWith (mempty, mempty, kv) "fireworks.jpg" mempty mempty)
+
+
     , "Uppercase extension" =:
       "[[file:test.PNG]]" =?>
       para (image "test.PNG" "" "")