add notice reference to message
sort message list by create at
refactoring and fixing error in unit test
Merge branch 'develop' of https://github.com/DonutWorks/Ari into show-which-notice-in-message-list

Conflicts:
	db/schema.rb
Merge pull request #281 from DonutWorks/show-which-notice-in-message-list

#270 add notice reference to message