Major version upgrade

1. Renamed all camel-case tags to lower-case with underscores. For example : <cackleComments> was renamed to <cackle_comments>. Camel-case tags attributes were renamed as well. This is a *breaking change*.
2. Added new set of tags for widgets :
- Gravatar [Avatar image URL, User profile URL]
- LiveJournal [Like Button, Repost Button]
- MailRu [Faces box, Groups box]
3. Updated README.md docs