support range of ruby version development dependencies

Support recommended ruby version-patchlevel and
also minimum version-patchlevel.

recommended: ruby-2.0.0-p247
minimum: ruby-2.0.0-p195

Changed to support better integration with travis-ci
which is usually one stable patch release behind
on Ruby.
travis-ci: specify language ruby and version 2.0.0

hopefully default node will be 0.10.x