Readme: Fixed C++ example code, due to API change in commit a138e6fbc3.

Readme.markdown

@@ -108,8 +108,8 @@ C++ language:
         QrSegment::makeSegments("3141592653589793238462643383");
     QrCode qr1 = QrCode::encodeSegments(
         segs, QrCode::Ecc::HIGH, 5, 5, 2, false);
-    for (int y = 0; y < qr1.size; y++) {
+    for (int y = 0; y < qr1.getSize(); y++) {
-        for (int x = 0; x < qr1.size; x++) {
+        for (int x = 0; x < qr1.getSize(); x++) {
             (... paint qr1.getModule(x, y) ...)
         }
     }