Updated README.txt + kraken.install now has db logging table, although logging is yet to be implemented.

* added hook_libraries_info (seems  to get registered properly
  too);

* use of libraries_detect to determine if library is available or
  to display libraries module's error message;

* added 'Kraken optimize' effect;

* stub function for effect callback.

* the api key and secret is now set at admin/config/media/image-toolkit
* README.txt added
* libraries module dependency added