Fix --include-dependencies parameter on RubyGems >= 2.0.0

Related to #2414

Since I'm not sure what version of RubyGems started making the `--install-dependencies` flag  the default, I've decided to include it in everything that won't break - i.e. every version before major version 2.  I also have the command now use the `--ignore-dependencies` flag, since this is, I assume, the expected behavior.