Update binscripts/rvm-installer

FreeBSD tar actually supports --strip-components, though it is not documented in `tar --help`. It is, however, in the manual:
     --strip-components count -(x mode only) Remove the specified number of leading path elements.  Pathnames with fewer elements will be silently skipped. Note that the pathname is edited after checking inclusion/exclusion patterns but before security checks.
Merge pull request #1585 from samaelszafran/patch-1

Update binscripts/rvm-installer