#Example of PostgreSQL's Array Feature in Rails
It includes only one model: Group, which has a tags field
tags field is declared as: t.text "tags", default: [], array: true
The input field accepts multiple tags separated by newline.
It removes duplicate tags when saving to database.
By default, Rails shows curly braces {} in the text input field of the form.
Check Group#formated method and _form.html.erb for the changes I made.
This example only works with Rails 4.2.0.rc1, but fails on 4.2.0
The testing code indicate that with Rails 4.2.0, the array could not create.