First versionof the book cover importer

It is very raw, not very performant and untested. But it is mostly
working.
HOTFIX: Adds mechanize to production as well
Display user's read books

Lists books that the user already read on the edit page.
Merge pull request #43 from groupbuddies/jj-list_read_books

Jj list read books
Clearance sing_up route hack https://github.com/thoughtbot/clearance/issues/415
Sign up page
Added sign_up page with tests
Code review fixes
More code review fixes
code review fixes
Fixes
Code review fixes
Merge pull request #44 from groupbuddies/jj-sign_up

Jj sign up
Refactored menu button and transitions
Only one configuration for travis
Extend loan period
Show extend button only when extendable

* Only shows one week before the ending of the loan
* Can only be extended once
Notifies user that she can only renew once

* Show the expiration date for a loan on my shelf