Columns marked for serialization do not serialize

Columns in an AR model can be marked for serialization if they are being used to store Arrays, Hashes, or other YAML-able data non-relationally:

class Hat < ActiveRecord::Base
  serialize :description
end

However, if this column is used for a variant/union type (such as a column used sometimes for strings, sometimes for arrays, and sometimes for hashes), data can become corrupted when it is deserialized on its way out of the database:

  1) Failure:
test_what_goes_in_comes_back_out(HatTest)
    [./test/unit/hat_test.rb:10:in `test_what_goes_in_comes_back_out'
     /Users/bryce/Documents/serialize_test/vendor/rails/activerecord/lib/../../activesupport/lib/active_support/testing/setup_and_teardown.rb:67:in `__send__'
     /Users/bryce/Documents/serialize_test/vendor/rails/activerecord/lib/../../activesupport/lib/active_support/testing/setup_and_teardown.rb:67:in `run']:
<"<span style=\"color: #800 FileStore can only store strings\">SODA HAT IS A SLANG TERM FOR A LID</span>\n"> expected but was
<{"<span style=\"color"=>nil}>.

A project demonstrating this can be found at: http://github.com/bkerley/serial...

The attached patch adds a test for this problem and provides a fix that passes rake test_sqlite3.