Fix warnings, upgrade to C++14

Signed-off-by: Micaela Verucchi <micaelaverucchi@gmail.com>

src/CenternetDetection.cpp

@@ -119,6 +119,7 @@ bool CenternetDetection::init(const std::string& tensor_path, const int n_classe
     dst2.at<float>(2,0)=dst2.at<float>(1,0) + (-dst2.at<float>(0,1)+dst2.at<float>(1,1) );
     dst2.at<float>(2,1)=dst2.at<float>(1,1) + (dst2.at<float>(0,0)-dst2.at<float>(1,0) );
     
+    return true;
 }