Use of #tap before requiring Active Support breaks on Ruby 1.8.6

Commit 945bf9c2 breaks Active Record on versions of Ruby that don't have a native #tap (like 1.8.6), because it tries to use #tap about two lines before Active Support is available :)

When I try to run the AR tests on OS X's 1.8.6p114, I get this:

/Users/chrisk/Documents/railstest/rails/activerecord/test/cases/../../lib/active_record.rb:24: undefined method `tap' for #<String:0x11ca1a0> (NoMethodError)

A simple fix is to go back to the previous way of handling the string, just using a local variable. This fixes the test suite for me. I've attached a patch.