Replace `std::endl` with `'\n'`

See [LLVM Coding Standards](https://llvm.org/docs/CodingStandards.html#avoid-std-endl)

pi2-demo/src/main.cpp

@@ -49,12 +49,12 @@ int main(int argc, char *argv[]) {
     po::notify(variablesMap);
 
     if (variablesMap.count("help") > 0) {
-      std::cout << "Usage: " + std::string(args.at(0)) +
-                       " [OPTION]... [FILE]\n"
-                       "Parses and simulates FILE according to the PI-2 of the "
-                       "RWTH.\n\n"
-                << visibleOptions << std::endl;
-      return 1;
+      std::cout
+          << "Usage: " << args.at(0)
+          << " [OPTION]... [FILE]\n"
+             "Parses and simulates FILE according to the PI-2 of the RWTH.\n\n"
+          << visibleOptions;
+      return 0;
     }
 
     if (variablesMap.count("input-file") > 0) {
@@ -77,16 +77,16 @@ int main(int argc, char *argv[]) {
                                         std::chrono::seconds(seconds);
 
         map.simulate(duration, timescale, refreshRate);
-        std::cout << "Simulation done!" << std::endl;
+        std::cout << "Simulation done!\n";
       } else {
-        std::cout << "Failed to open " << nativePathname << std::endl;
+        std::cout << "Failed to open " << nativePathname << '\n';
         return 1;
       }
     } else {
       std::cout << "Input file was not set.\n";
     }
   } catch (std::exception &e) {
-    std::cout << e.what() << std::endl;
+    std::cout << e.what() << '\n';
     return 1;
   }
 }