Dependency Updates

Thanks for creating this gem - it's a big help.

I've made a couple tweaks based on changes to dependencies. Each change is contained within its own commit.

* Removed the debugger gem dependency - this gem is not supported on Ruby 2.0 or greater.
* Explicitly set the version of the capistrano gem to be less than 3. This gem is clearly for Capistrano, and capistrano 3 has been released since this gem was created.
* Fixed a broken spec due to an update to the AWS SDK for Ruby.

Thanks,
Brian