add option and two helper methods (seed! and seed_once!) to validate models on save
Merge branch 'master' of https://github.com/codez/seed-fu into codez-master

* 'master' of https://github.com/codez/seed-fu:
  add option and two helper methods (seed! and seed_once!) to validate models on save

Conflicts:
	lib/seed-fu/seeder.rb