Extend Coupon with new properties

According to documentation http://docs.recurly.com/api/coupons.
copyright: update copyright header date

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
stylre: remove wildcard imports

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
model: fix boolean parsing

The Map from Jackson has two elements, for the type and the value.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
test: fix TestCoupons

There are only 5 coupons in the payload, not 11.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
CREDITS: add entry for Lebid Yuriy

Thanks!

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>