Add support for progress callbacks of data requests.
Merge pull request #102 from arnaudjbernard/master

Add support for progress callbacks of data requests.
Removing unnecessary explicit newValue argument on setter
[Issue #70] Removing subdelegate after didCompleteWithError delegate method, to allow for deallocation with Request
[Issue #89] Fixing authentication challenge handling
Making detail view controller table view not selectable
Adding HTTPBinAPIEndpoint enum for routing
Minor cleanup and refactoring
Removing commented-out NSJSONWritingOptions code
Adding authentication tests
Minor formatting
Fixing download tests
Minor reformatting
Set download delegate error on failed move to destination
Adding tests for Printable and DebugPrintable
Including delegate credential in cURL representation
Fixing authentication challenge implementation to cancel after failed attempt
Update README.md
Exposing session and task properties
Making SessionDelegate private