- removed jruby specific workaround (this was fixed in ruby-build https://github.com/sstephenson/ruby-build/commit/76b632892b8811ea422ca2078db137463ae59cd7)

- removed the default inclusion of the 'global' gemset, rbenv-gemset is a tool for clearly defined gemsets, so no gemset should be "enforced". If the user really wants the global gemset included, it's easy to do so by including 'global' gemset in either the .rbenv-gemsets file or in the RBENV_GEMSETS env variable (fixes jf/rbenv-gemset#59)