I tried to install YouCompleteMe on Mac for vim, but I\'ve been using the system vim which is version 7.3. I tried to update my vim using homebrew by typing brew install v
You're loading your system vim first, as you can see by which vim returning /usr/bin/vim instead of /usr/local/bin/vim.
/usr/local/bin is homebrew's path.
Make sure that your path lists /usr/local/bin before /usr/bin:
/usr/local/bin:/usr/bin
This will allow homebrew's vim to be sourced before the system vim.
To view your path:
echo "$PATH"