Unescape entities in writing CSL JSON.

The renderCslJson function escapes `<`, `>`, and `&` as entities.
This is appropriate when generating HTML, but in CSL JSON
these are supposed to appear unescaped.

Closes jgm/citeproc#17.

src/Text/Pandoc/Writers/CslJson.hs

@@ -23,6 +23,7 @@ import qualified Data.Text as T
 import qualified Text.Pandoc.UTF8 as UTF8
 import Text.Pandoc.Error
 import Text.Pandoc.Class
+import Text.Pandoc.XML (fromEntities)
 import Control.Monad.Except (throwError)
 import Data.ByteString.Lazy (toStrict)
 import Data.ByteString (ByteString)
@@ -84,5 +85,7 @@ toCslJson locale = toStrict .
   encodePretty' defConfig{ confIndent = Spaces 2
                          , confCompare = compare
                          , confNumFormat = Generic }
-  . map (runIdentity .  traverse (return . renderCslJson locale . foldMap fromInline))
-
+  . map (runIdentity .  traverse (return .
+                                  fromEntities .
+                                  renderCslJson locale .
+                                  foldMap fromInline))

test/command/citeproc-17.md

@@ -0,0 +1,17 @@
+```
+% pandoc -t csljson
+---
+references:
+- id: foo
+  type: book
+  title: "Hi & Low"
+...
+^D
+[
+  {
+    "id": "foo",
+    "title": "Hi & Low",
+    "type": "book"
+  }
+]
+```