Ideally, we should find a way to make this work with 2.99 as well, so that we can issue a "change to the `rspec-autotest`" warning from rspec-core 2.99 when the autotest stuff is used, and users can switch to the gem to silence the warning...and then upgrade to rspec 3.  Is there an easy way to make this work on 2.99 in spite of rspec-core 2.99 having autotest support as well?