Init more thread friendly

- Retrieval of URLForUbiquityContainerIdentifier set to run async
inside init-method.
- Avoided multiple calls to URLForUbiquityContainerIdentifier by using
instance variable
- refined instructions to setup singleton to avoid initializing twice
Init more thread friendly

- Retrieval of URLForUbiquityContainerIdentifier set to run async
inside init-method.
- Avoided multiple calls to URLForUbiquityContainerIdentifier by using
instance variable
- refined instructions to setup singleton to avoid initializing twice
Update README.md
Re-closing of UIDocument avoided
Avoided re-closing document
removed obsolete "saveChangesToDocumentWithName:"

(Was a fuunctional duplicate of saveAndCloseDocumentWithName:)
Changed saveChangesToDocumentWithName: to be deprecated instead of just deleting it
Little fix in documentation

@param for iCloudDidFinishInitializingWitUbiquityToken: fixed.
Documentation recompiled.
Merge pull request #24 from JackJackBauer/master

Version 7.1

Changes to thread-management, initialization, and document saving