Updated README.md with latest Ruby
For "zoquetes" like me

I was not sure where to add these lines, maybe there are more people like me out there.
Merge pull request #27 from fguillen/patch-1

For "zoquetes" like me
Added 'rbenv-gem-rehash' to plugins list.
Suggest installing Ruby 2.1.0
Merge branch 'master' of https://github.com/fesplugas/rbenv-installer