fix bug about issue #155
bug fixed about submitting without file
bug fixed about column name is blank
Merge branch 'develop' of https://github.com/DonutWorks/Ari into fix-bug-about-issue-#155

Conflicts:
	app/controllers/admin/import_controller.rb
Merge pull request #170 from DonutWorks/fix-bug-about-issue-#155

Fix bug about issue #155
merge with develop branch