change database posgresql to sqlite3
ISSUE-1 fix user_spec
ISSUE-2 fix devise configuration
ISSUE-3 fix categories_controller errors with admin presence
ISSUE-4 play with product validations
ISSUE-5 fix spec for category model
ISSUE-6 fix specs for Review model
ISSUE-7 deal with ProductsController
ISSUE-8 ReviewDecorator fix
ISSUE-2 fixes with devise and registration
ISSUE-9 check if each review is assigned to user who wrote it
ISSUE-10 hide inaccessible links
ISSUE-11 add links in navigation bar
ISSUE-13 add some css