paypal/meddleware — pull request #1 by totherik (2014-01-28 22:23:16+00:00)
Title: add parallel, race, and fallback support

##### Parallel
Add a `parallel` property with middleware spec definition object to have middleware executed in parallel.

##### Race
Add a `race` property with middleware spec definition object to have the first completing middleware complete fulfill the placeholder and advance the middleware chain.

#### Fallback
Add a `fallback` property with middleware spec definition object (and priorities) to execute each moddleware in serial until one completes successfully.

TODO: Docs.