#4
Helper added to show 404 error, `not_found` error handled.
#4
 - 404 is well designed, now.
 - 500 added.
 - `error.erb` layout added.
#4I just did some enhancement on 500.erb and tried to move helpers into a separate file.
Re-structure the app.
Works with rack
#4
Code cleaned up, 500 error page fixed.
Merge pull request #6 from laze/feature/4-add-error-pages

Feature/4 add error pages