Correct Recurly module project description

On the project's main page, the following needs correction:

Each account can only be subscribed to a single plan, although Recurly does simplify the process of canceling and / or upgrading plans, including pro-rated credits or charges as the case may require.
Subscription plans are presumed to be open ended, so you cannot setup a subscription through their service alone to only recur a limited number of times.

Each account can have multiple subscriptions now.

Subscriptions can be set to end after a specific number of billing cycles (and not automatically renew) by setting the total_billing_cycles on the initial subscription. From Recurly docs:

total_billing_cycles Renews the subscription for a specified number of cycles, then automatically cancels. Defaults to the subscription renewing indefinitely.

@see the related task How to handle subscription total_billing_cycles and first_renewal_date subscription params