MultiRails 0.0.4

MultiRails is an open source development tool that will enable Rails developers to easily test gems and plugins against multiple versions of Rails.
MultiRails Integrates with your continuous integration easily with a Rake task to test against many versions.

Main features:>
- easily test plugins/extensions using a require from your test_helper.rb and a require in your RakeFile
- rake tasks to test against a specified version of Rails, the latest version, or all versions
- tentative support for testing plain Rails apps against multiple versions of Rails
- uses rubygems for version management of Rails

Enhancements:
- change the all task so that the build will run through all rails versions, even if one of them fails, but at the end the failing versions are printed and we abort. Thanks to Evan Weaver for initial patch and idea.
- display the rails gem from the load path as a sanity check right after we gem/require
- add autotest rails plugin discovery, so I can use autotest to test multi_rails
- various rake tweaks to make release easier and more automated