Merge pull request steipete#56 from stefanhp/master

Added support for OS X

Merge pull request steipete#48 from happybits/master

Refactor to work with AFNetworking 2.0 version

document manual trunication

Fixes a warning in Xcode5

Merge pull request steipete#25 from nhisyam/master

Added reference to AFDownloadRequestOperation in progressiveDownloadProgressBlock