- add wait-time between HTTP requests similar to exhentai
- add 'wait-min' and 'wait-max' options
- increase retry-count for HTTP requests to 10
- implement user authentication (non-authenticated users can only view
images up to page 25)
- implement 'skip()' functionality (only works up to page 50)
- implement image-retrieval for pages >= 51
- fix issue with multiple tags