Add column `fixed' on payments, categories
Add database_cleaner
Add pry
subcategory -> sub_category
Add factory_girl
Enable factory_girl
Add factories

- spec/factories/category
- spec/factories/payments
- spec/factories/sub_categories
Use factory_girl 4.2.0
spec: Log SQL when metadata[:ar_log] is true
spec: reload factories at first for Spring
Payment#category: see category through sub_category
Use bootstrap
Hamlize layout
remove view specs
Use bootstrap on layout
Serialize `meta` columns
migration: Set default values on tables
Add validates_presence_of on models
Add DatetimeParameterHandler
Payment#paid_at: default to `Time.now`