Tagging doesnt need a user yet

- removed user references on tagging
- adjusting code/test to not handle a user on tagging join model
Creating service object to build a link

- it parses the link and extract tags
- first implementation.. find a way to separate the possible tokens,
  because it can grow bigger (maybe reminder, share, etc)
Small refactoring on tests name
allowing to add tags to links

- it shows all tags that a link has
- it allows to create a new link with some tags