Added Id case class to be used for id's.

* At the moment only uuid id's are supported.
* Added type mapper from Id to UUID
Merge branch 'master' of https://github.com/dre1080/slick-additions

# By andoooooo
# Via andoooooo
* 'master' of https://github.com/dre1080/slick-additions:
  Update README.md
  Update README.md