deprecate old Writers

also, use withers instead of setters, and update docs
diff --git a/src/jsontestrunner/main.cpp b/src/jsontestrunner/main.cpp
index 28894ce..3a2229c 100644
--- a/src/jsontestrunner/main.cpp
+++ b/src/jsontestrunner/main.cpp
@@ -185,7 +185,7 @@
     Json::Value const& root)
 {
   Json::StreamWriter::Builder builder;
-  builder.setCommentStyle(Json::StreamWriter::CommentStyle::All);
+  builder.withCommentStyle(Json::StreamWriter::CommentStyle::All);
   return writeString(root, builder);
 }
 static int rewriteValueTree(