Click on the first matching product link

Both the image and the text link are matched and clicking on either is
fine, so do it.

This fixes issue spree-contrib#176.

spec/features/paypal_spec.rb

@@ -47,7 +47,7 @@ def within_transaction_cart(&block)
 
  def add_to_cart(product)
  visit spree.root_path
- click_link product.name
+ click_link product.name, match: :first
  click_button 'Add To Cart'
  end