Update React-Router from 2.0.0 to 2.5.2

[TzolkinB]

If you use react-router 2.0.0, you will get multiple warnings in the console. To avoid this, install react-router 2.5.2 instead.

If you already installed version 2.0.0, stop the server, and run npm uninstall [email protected] then run npm install --save [email protected]. When you restart the server npm start, the errors should be gone.