If you are using a combination of Vim (or MacVim), Zsh and RVM you might run into an issue where ruby -v in the terminal spits out ruby-2.2.0 but you see this message when running rails.vim commands in Vim:

Your Ruby version is 2.0.0, but your Gemfile specified 2.2.0

If you are determined enough you might find this page, which describes a few situations and fixes for integrating Vim and RVM, but the solution to this particular issue is somewhat buried and unclear. TLDR fix: Add the following line to your .zshenv file:

source $HOME/.rvm/scripts/rvm

This is necessary because Vim isn’t going to read the dotfiles where you sourced RVM initially; see here for more info.