Added German Localization with Warning
Merge pull request #781 from JeanetteMueller/master

Added German Localization with Warning
Update Localizable.strings

spelling correction
Merge pull request #782 from JeanetteMueller/patch-2

Update Localizable.strings
Refactored code to show 1-button alert views
Localized hardcoded strings
Removed german localisation

See #664 for more info on the rationale for the decision.
Added CONTRIBUTING file
Removed local cache for getCover function
Update existing issues when refreshing shelf

Closes #547.
Fix: avoid downloading covers a million times

Downloaded shelf covers will be returned from a local cache unless the user has explicitly refreshed the shelf.
Moved postAPNSToken function to BakerAPI singleton
Added getShelfJSON function to BakerAPI
Added getPurchasesJSON function to BakerAPI
Added postPurchaseReceipt function to BakerAPI
Refactored and improved BakerAPI
Fix: restore cache policy for Shelf API call
Moved UUID functions to BakerAPI
Encapsulate all API calls into BakerAPI
Better BakerAPI error management for status != 200