RNFR checks that RNTO was called
Tests use fork of double-bag-ftps for ruby-2.0 compatability

There is a pull request for the original gem.  Switch back to the
original gem once it accepts the patch or otherwise starts working
with ruby 2.0,
Readme notes known-good versions of Ruby
Version bump to 0.2.1
Regenerate gemspec for version 0.2.1