Merge branch '48-user-rating-system' into 'master'

documents/database-description/database-schema.mwb

src/db/create_tables_load_content.sql

src/db/database-create_postgre.sql

src/web/app.js

src/web/helpers/helpers.js

src/web/helpers/user.js

src/web/public/images/user_avatars/0.png

src/web/public/stylesheets/style.css

src/web/routes/book.js

src/web/routes/index.js

src/web/views/details.hbs

src/web/views/layouts/layout.hbs