404 Page

According to <a href = "https://trello.com/c/RZb3nmnr">Trello</a> a better 404 page was one of the bugs and small fixes people could contribute to. I added the path that caused the 404 page, added a link back to the home page, and added a 404 message. 

This is my first time trying to contribute to an open source project so let me know if I did anything wrong or anything. Thanks!