Write module documentation READMEs

This documentation looks good to me so far. I'm walking through it now.

Maybe add a step to make sure "Payment UI" is enabled.

Also I'm to lazy but I think there are a couple of other documentation issue for this project open. Maybe you could search and see if we can consolidate them all here since you have the most substantial amount of information.

Shouldn't it also include a list of the php5 modules that need to be installed for it work?

Like making sure curl is enabled?

This documentation patch looks good, but will need quite a few updates once the beta release is prepared (ie: #1250424: Improve support for multiple prior authorization captures and others)

Closed #1108650: Document How to use Paypal WPS Module as a duplicate in favor of this thread.

I'm not sure it makes sense to keep full documentation in code; why not just a handbook page here on d.o?

Also, we need to update the docs to indicate that PayPal WPP requires the default billing address to process transactions per #1772362: EntityMetadataWrapperException: Unknown data property commerce_customer_address. in EntityStructureWrapper->getPropertyInfo().

I've updated the project page with all the information we could possibly need. Eventually we'll want to split this out into a much more user friendly guide with screenshots; I'll talk with joshmiller about it and see where he is w/ Commerce Kickstart docs. : )