Added comments in examples

examples/JsonGeneratorExample/JsonGeneratorExample.ino

@@ -13,12 +13,36 @@ void setup() {
     // wait serial port initialization
   }
 
+  // Memory pool for JSON object tree.
+  //
+  // Inside the brackets, 200 is the size of the pool in bytes.
+  // If the JSON object is more complex, you need to increase that value.
   StaticJsonBuffer<200> jsonBuffer;
 
+  // StaticJsonBuffer allocates memory on the stack, it can be
+  // replaced by DynamicJsonBuffer which allocates in the heap.
+  // It's simpler but less efficient.
+  //
+  // DynamicJsonBuffer  jsonBuffer;
+
+  // Create the root of the object tree.
+  //
+  // It's a reference to the JsonObject, the actual bytes are inside the
+  // JsonBuffer with all the other nodes of the object tree.
+  // Memory is freed when jsonBuffer goes out of scope.
   JsonObject& root = jsonBuffer.createObject();
+
+  // Add values in the object
+  //
+  // Most of the time, you can rely on the implicit casts.
+  // In other case, you can do root.set<long>("time", 1351824120);
   root["sensor"] = "gps";
   root["time"] = 1351824120;
 
+  // Add a nested array.
+  //
+  // It's also possible to create the array separately and add it to the
+  // JsonObject but it's less efficient.
   JsonArray& data = root.createNestedArray("data");
   data.add(double_with_n_digits(48.756080, 6));
   data.add(double_with_n_digits(2.302038, 6));