Added comments

JsonGenerator/JsonPrintable.h

@@ -13,16 +13,27 @@ namespace ArduinoJson
 {
     namespace Generator
     {
+        // Contains methods to generate a JSON string.
+        // Implemented by both JsonObject and JsonArray
         class JsonPrintable : public Printable
         {
         public:
 
+            // Generates the compact JSON string and sends it to a Print stream 
             virtual size_t printTo(Print& p) const = 0;
 
+            // Generates the compact JSON string and writes it in a buffer
             size_t printTo(char* buffer, size_t bufferSize) const;
 
-            size_t prettyPrintTo(IndentedPrint& p) const;
+            // Generates the indented JSON string and sends it to a Print stream
             size_t prettyPrintTo(Print& p) const;
+
+            // Generates the indented JSON string and sends it to a IndentedPrint stream
+            // This overload allows a finer control of the output because you can customize
+            // the IndentedPrint.
+            size_t prettyPrintTo(IndentedPrint& p) const;
+
+            // Generates the indented JSON string and writes it in a buffer
             size_t prettyPrintTo(char* buffer, size_t bufferSize) const;
         };
     }