Hooks up rake test

Splits out class so testing won't create a task / can find the file with .rb extension
Renames test file so it's picked up by rake test
Moves Ruby logic to lib
@zenspider It looks like the original otask.rb was in class 'Otask' and the actual otask logic was in class 'OTask'. I looked at some other gems and just changed the original otask.rb to a version.rb and replaced it in the rake files. I'd love to get your feedback on this change!