Add "overwrite" option to the handle() method in mux

This allows to add several method (POST,DELETE,PUT) to an existing handler without headache
or having to keep a reference to every handle

src/served/multiplexer.cpp

@@ -121,14 +121,22 @@ multiplexer::get_segments(const std::string & path)
 //  -----  http request handlers  -----
 
 served::methods_handler &
-multiplexer::handle(const std::string & path, const std::string info /* = "" */)
+multiplexer::handle(const std::string & path, const std::string info /* = "" */, bool overwrite)
 {
+
 	// Remove any duplicates.
 	for ( auto it = _handler_candidates.begin(); it != _handler_candidates.end(); )
 	{
 		if ( std::get<2>(*it) == path )
 		{
-			it = _handler_candidates.erase(it);
+				if(overwrite)
+				{
+					it = _handler_candidates.erase(it);
+				}
+				else
+				{
+					return std::get<1>(*it);
+				}
 		}
 		else
 		{

src/served/multiplexer.hpp

@@ -139,7 +139,7 @@ class multiplexer
 	 *
 	 * @return returns a methods_handler used to specify handlers per HTTP method
 	 */
-	served::methods_handler & handle(const std::string & path, const std::string info = "");
+	served::methods_handler & handle(const std::string & path, const std::string info = "", bool overwrite = true);
 
 	//  ----- request forwarding  -----