Ensure that zsh autocompletion won't be broken after invoking `__rvm_unload` by cleaning up `$fpath` before the meat of the `__rvm_unload` function; this will prevent the rest of the code from nuking `$fpath` altogether.
Correctly infer `$rvm_user_install_flag` when performing a root-only install according to instructions on FAQ.
Merge pull request #1845 from JoeKun/rvm-installer-root-only-install-confusion

rvm-installer still believes it's performing a multi-user install when installing for root only
Merge pull request #1838 from JoeKun/master

Ensure that zsh autocompletion won't be broken after invoking __rvm_unload`