add Rails 4 to compatibilty in README
drop 1.8.7, ree and 1.9.2 from travis
minimum Ruby 1.9.3
no need to be strict on nokogiri version now that we're on 1.9.3 only
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
Whitelist only `for` and `class` attributes on BooleanInput label.

I can't find a decent reason to be merging with `input_html_options` and fussing around with it like it was.

Closes #995
Allows to disable model infered class from form
Renames variable, adds tests and documentation
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 pull request #1016 from justinfrench/whitelist-boolean-label-html-options

Whitelist only `for` and `class` attributes on BooleanInput label.
Configure model class through a proc
Merge pull request #986 from groupbuddies/master

Allows to disable model infered class from form
bump version to 2.3.0.rc3
add failing spec and fix rails version check