remove Rails 3.0 and 3.1 from Appraisals
require actionpack >= 3.2
drop 3.0 and 3.1 from .travis.yml
drop Rails 3.1 code path for CSS files in install generator
fix generator comment
rails 3.1 introduced button_tag, no need for work-around
Merge branch 'master' into drop-rails-30-and-31

Conflicts:
	gemfiles/rails_3.0.gemfile
	gemfiles/rails_3.1.gemfile
bump actionpack dependency to 3.2.13
Merge branch 'master' into drop-rails-30-and-31
remove unneccessary hidden input
deprecate rails < 4.0.4
Merge pull request #950 from justinfrench/drop-rails-30-and-31

Drop support for Rails < 3.2.13