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
Import book from goodreads

Import a book from www.goodreads.com given a ISBN.
Added goodreads and webmock gems to the project
It imports:
* ISBN
* Title
* Authors
* Cover image
* Number of pages
* Descripton
Merge pull request #45 from groupbuddies/jj-import-from-goodreads

Import book from goodreads
Extracted responsibilities from book controller
Added reviews counter_cache
Merge pull request #49 from groupbuddies/jj-review-counter-cache

Added reviews counter_cache
Added .env to Capistrano's list of linked files
Added dotenv-rails gem to production as well