Added service factory foundation class
Added HTTP client foundation class
Implemented main API calls
Removed conversion warnings
Implemented 500px photo search
Class renaming
Added basic Flickr implementation
Removed crypto sha1 conversion
Minor refactoring
Added API classes documentation
Improved Flickr tag & photo search implementation
Stopped any loading request when dimissing picker
Implemented Flickr image url methods
Created DZNPhotoTag model data to encapsulate tags.
Implemented DZNPhotoTag parsing.
Moved the photo & tag parsing inside of their clients
Added assert check when register other services than 500px and flickr
Removed 500px & Flickr api wrapper pod
Update tests
Added content description of DZNPhotoMetadata & DZNPhotoTag classes.