No need for dependency graph to be in one queue

From https://developer.apple.com/library/ios/documentation/General/Conceptual/ConcurrencyProgrammingGuide/OperationObjects/OperationObjects.html (look for “Configuring Interoperation Dependencies”):

> Dependencies are also not limited to operations in the same queue. Operation objects manage their own dependencies and so it is perfectly acceptable to create dependencies between operations and add them all to different queues.

I have to admit that I have used such behaviour only once some time ago (producers-consumers situation, and I need to keep them under different concurrency constraints), so maybe you have included that warning for some reason I don’t know.
Grammar fix

Removed redunant wording
Fix miscapitalization
Merge pull request #184 from lutaaya/patch-2

Fix miscapitalization
Merge pull request #182 from drodriguez/patch-1

No need for dependency graph to be in one queue
Merge pull request #183 from drakecaiman/master

Grammar fix
Stashing
Resetting categories
Changing description to excerpt
Stashing
Assorted metadata and content fixes
Adding article for XCTestCase
Removing ratings from metadata
Cleaning up conflicts in NSOperation article
Removing unnecessary published: true from metadata
Removing ref metadata
Removing HTML tags from excerpts
Updating categories
Remove erroneous ‘an’ in XCTest article.
Adding Swift Documentation article