Add coupon logic (1st step)
Add coupon logic (2st step) - Observer added - now Client.balance is automaticaly decreased on coupon addition
coupon number uniqueness
Merge branch 'feature-coupon-add' into develop
hot fix: wrong redirect after coupon save error
hot fix: coupon number validator 13 digits
hot fix: better error messages
hot fix: better error messages 2
hot fix: real client balance
hot fix: client buyable coupons count
hot fix: super
Merge remote-tracking branch 'origin/develop' into develop

Conflicts:
	app/models/event.rb
	db/development.sqlite3