fix migration

these columns already exist at this point
remove default boolean values for item's iva and ice. This fixes #13
Change retencion's default value for `fecha_emision`. Closes #8
name validations on category and item

and make items dependent on category
added spec_helper
added `rake db:dummy`
added `dotenv-rails`
added dummy environment
refactored schedule.rb
Merge branch 'master' into stable