Add missing change

Update README and one missing line for generator

README.md

@@ -2,6 +2,7 @@
 This is a C# library for working with JavaScript source maps and deminifying JavaScript callstacks.
 
 ## Source Map Parsing
+The `SourcemapToolkit.SourcemapParser.dll` provides an API for parsing a souce map into an object that is easy to work with and an API for serializing source map object back to json string. 
 The source map class has a method `GetMappingEntryForGeneratedSourcePosition`, which can be used to find a source map mapping entry that likely corresponds to a piece of generated code. 
 
 ## Call Stack Deminification

src/SourcemapToolkit.SourcemapParser/SourceMapGenerator.cs

@@ -61,6 +61,7 @@ namespace SourcemapToolkit.SourcemapParser
         /// </summary>
         public string SerializeMapping(SourceMap sourceMap)
         {
+            return SerializeMapping( sourceMap, null /* jsonSerializerSettings */ );
         }
 
         /// <summary>