cancan => cancancan
Simplify/improve model specs
Improve/simplify auth specs
Modify controllers for cancancan. Improve/simplify expenses/incomes specs and controllers.
Extract common expense/income bits into parent controller
Change validation rules to disallow 0 for both expenses and incomes
Fix expense/income specs amount specs
Collapse common parts from expense/income controllers
Merge branch 'controllers_v3'