Add cancelFetch to entity protocol
NSHTTPURLResponse extension
First go at NetworkEntity (without tests)
Add OHHTTPStubs as submodule
Fix bug in hnk_validateLengthOfData
First test using OHHTTPStubs
Test validateLengthOfData
Further NetworkEntity tests
Check if image is valid
Merge pull request #66 from Haneke/feature/entities/network

Network entity. Closes #45.