15: updated docs
15: updated docs

Task-Url: http://github.com/LorenzoBettini/packtpub-xtext-book-2nd-examples/issues/15
LorenzoBettini/packtpub-xtext-book-2nd-examples,LorenzoBettini/packtpub-xtext-book-2nd-examples,LorenzoBettini/packtpub-xtext-book-2nd-examples,LorenzoBettini/packtpub-xtext-book-2nd-examples