Income and Expense added in routes and in the Invoice model.

Files Modified:

modified:   app/assets/stylesheets/bootstrap_and_overrides.css.scss
modified:   app/controllers/invoices_controller.rb
modified:   app/helpers/application_helper.rb
deleted:    app/helpers/facturas_helper.rb
new file:   app/helpers/invoices_helper.rb
modified:   app/views/invoices/index.html.haml
modified:   app/views/invoices/new.html.haml
modified:   app/views/layouts/_navbar.html.haml
modified:   config/routes.rb
new file:   db/migrate/20130824005408_add_type_to_invoice.rb
modified:   db/schema.rb