Updating appraisal, adding test.
attribute_change read attribute in handled manner

* lib/safe_attributes/base.rb (attribute_change): instead of punting we
try to read the attribute in a way that supports missing attribute
methods
* spec/safe_attributes/safe_attributes_spec.rb: added some of the basic
dirty tests from activerecord to cover attribute_change
Add missing appraisal files
Preparing for release
Update Gemfile, appraisals
Tested against jruby 1.7.2