Switch from pretty-simple to pretty-show for native output.

Update tests.

Reason:  it turns out that the native output generated by
pretty-simple isn't always readable by the native reader.
According to https://github.com/cdepillabout/pretty-simple/issues/99
it is not a design goal of the library that the rendered values
be readable using 'read'.  This makes it unsuitable for our
purposes.

pretty-show is a bit slower and it uses 4-space indents
(non-configurable), but it doesn't have this serious drawback.

1 files changed, 35 insertions, 29 deletions

diff --git a/test/command/168.md b/test/command/168.md
index 02b426089..acd42b97d 100644
--- a/test/command/168.md
+++ b/test/command/168.md
@@ -12,23 +12,23 @@ nested div
 :::::::::::::::::::::::::::::::
 ^D
 [ Div
-  ( "", [ "warning" ], [] )
-  [ Para
-    [ Str "This"
-    , Space
-    , Str "is"
-    , Space
-    , Str "the"
-    , Space
-    , Str "warning!"
+    ( "" , [ "warning" ] , [] )
+    [ Para
+        [ Str "This"
+        , Space
+        , Str "is"
+        , Space
+        , Str "the"
+        , Space
+        , Str "warning!"
+        ]
+    , OrderedList
+        ( 1 , Decimal , Period )
+        [ [ Plain [ Str "list" ] ] , [ Plain [ Str "another" ] ] ]
+    , Div
+        ( "myid" , [ "class" ] , [ ( "key" , "val" ) ] )
+        [ Para [ Str "nested" , Space , Str "div" ] ]
     ]
-  , OrderedList
-    ( 1, Decimal, Period )
-    [ [ Plain [ Str "list" ] ], [ Plain [ Str "another" ] ] ]
-  , Div
-    ( "myid", [ "class" ], [ ( "key", "val" ) ] )
-    [ Para [ Str "nested", Space, Str "div" ] ]
-  ]
 ]
 ```
 
@@ -38,7 +38,14 @@ foo
 :::
 bar
 ^D
-[ Para [ Str "foo", SoftBreak, Str ":::", SoftBreak, Str "bar" ] ]
+[ Para
+    [ Str "foo"
+    , SoftBreak
+    , Str ":::"
+    , SoftBreak
+    , Str "bar"
+    ]
+]
 ```
 
 ```
@@ -50,18 +57,17 @@ And another.
 :::::
 ^D
 [ Div
-  ( "", [ "Warning" ], [] )
-  [ Para
-    [ Str "Here"
-    , Space
-    , Str "is"
-    , Space
-    , Str "a"
-    , Space
-    , Str "paragraph."
+    ( "" , [ "Warning" ] , [] )
+    [ Para
+        [ Str "Here"
+        , Space
+        , Str "is"
+        , Space
+        , Str "a"
+        , Space
+        , Str "paragraph."
+        ]
+    , Para [ Str "And" , Space , Str "another." ]
     ]
-  , Para
-    [ Str "And", Space, Str "another." ]
-  ]
 ]
 ```