Merge tag '0.9.10' into develop

Refactored cache to use NSOperationQueue for scheduling downloads; refactored code base to increase readability and maintainability
Added method for canceling requests for a given URL
Executing fail blocks if download operations haven't been started due to cancel state
Increased version to 0.9.10.1
Removed unnecessary interface definitions of private methods
Merge pull request #30 from artifacts/develop

Added cancelRequestsForURL: method; Executing fail blocks if download operations haven't been started due to cancel state; Code cleanup