Recursive folders

* Allow recursive traversing of folders with -r flag
* Print useful error in case of no image found
* Fixes issues 4 & 6

src/imageselector.h

@@ -9,15 +9,17 @@ class ImageSelector : public QObject
 {
     Q_OBJECT
 public:
-    ImageSelector(MainWindow& w, unsigned int timeout, std::string path);
+    ImageSelector(MainWindow& w, unsigned int timeout, std::string path, bool recursive);
     void start();
 
 public slots:
     void updateImage();
 private:
+    QStringList listImagesRecursive();
     MainWindow& window;
     unsigned int timeout;
     std::string path;
+    bool recursive;
     QTimer timer;
 };