Merge pull request #12 from mikepence/master

Tying to ActiveMerchant ~> 1.5.1
md: fix bummp 0.3.8
ad: Mike Pence to contributors. thx! :D
rm: gemset
:fix gem dependency should be less restrictive
Added referrerCode in SetPaymentOptions request (useful to track transactions in case of partnerships with PayPal)
Merge pull request #16 from njvitto/patch-1

Added referrerCode in SetPaymentOptions request
bump: to 0.3.11, remove nodocs and added njvitto to contributors
Added option action_type to support PAY_PRIMARY delayed chained payments
Merge pull request #18 from eldoy/master

Added option :action_type
ad: eldoy to contributors
bump to 0.3.11
Add displayOptions support to SetPaymentOptions request
Add receiverOptions support to SetPaymentOptions request
Fix README typos
Add basic documentation for #build_adaptive_set_payment_options_request to README
Merge pull request #19 from herimedia/more-set-payment-options

Add displayOptions and receiverOptions support to SetPaymentOptionsRequest
md: bump to 0.3.12
ad: Niels Ganser to contributors
Added option displayMaxTotalAmount to build_preapproval_payment to display amount with paypal on payment