refactorin normalization using raise and rescue
merge with develop branch
change empty error to raise and rescue
little typo
Merge branch 'develop' of github.com:DonutWorks/Ari into refact/catch-raise-and-set-validation

Conflicts:
	app/controllers/admin/import_controller.rb
Merge pull request #182 from DonutWorks/refact/catch-raise-and-set-validation

refactoring normalization using raise and rescue