Improved error message on reset password

When you try to reset your password and leave the password blank,
you now get an understandable error.

Resolves #11.
Fix error styling

Also changes main font.

Resolves #10.
Improved reset password form UI

Resolves #9
Add a show action for books
Added cover image uploading
Set up Heroku to use Unicorn
Merge branch 'master' into covers
Add remote cover uploading
pullin
merge