Improve messages on book display page.

First check if user owns the book - if yes disable button.
Then check if book is borrowed - if yes disable button.
Add book status info to book list.
After login and logout redirect user to home page instead /admin.
Prepare for Heroku deploy.
Bugfix - static files missing on Heroku
setup local development environment
add basic README file
Tighten security - only owners can edit books.

In the admin interface, every user can see only books he has added.
Also, malicious users who try to guess book id, are not allowed to
see those books (404 is returned).