Check Rails version before accessing ::Rails::Railtie

[sgronblo]

When requiring simplecov in a Rails 2 project, I get an uninitialized constant error due to ::Rails::Railtie. If I comment out the part that loads the railtie.rb file, code coverage generation works fine. Maybe you could define the Rake task in a different way if using Rails 2 or simply refrain from defining it if RailsTie is uninitialized?

[colszowka]

Damn, that's a big regression. Will fix it today and release a new gem.

[colszowka]

Just pushed 0.6.1 to Rubygems.org, should resolve this.