refactor: renaming functions and removing old functions

src/main.cpp

@@ -18,8 +18,8 @@ int main () {
 			std::ref(running));
 
 	while (running) {
-		body.collision(head);
-		body.add_tail();
+		body.check_collision(head);
+		body.check_new_tail();
 		if(body.m_body.size() >= (ROW * COL)) {
 			std::cout << "You win! Score: " + std::to_string(body.m_body.size()) << std::endl;
 			running = false;