remove superfluous quotes. optimize find calls.

A fair bit of the quoting used in thie script was unnecessary, so
I've taken the liberty of clearing that up to reduce line-noise.

The exiting method to populate the RUBIES array used some unnecessary
forks, so I've switched to a process substitution and a single call to
`find'. This approach still cannot handle paths with embedded newlines
but that edgecase requires GNU find's -print0 or more ugly forks with
-exec printf '%s\0' which defeats the purpose. If GNU find is expected
then altering this to be completely safe is a matter of add -d'' to
the read loop and -print0 to the find args. I've also used an array
to store the args to `find' in order to reduce the line length
considerably. IMO, a better approach would be to use 2-space tabs
instead to reduce the horizontal screen space wasted by excessive
indentation.

As per best practices guidelines, I've also changed the RUBIES var
to `rubies' instead. All-caps variable names are conventionally
reserved for environment variables and shell builtin variables. This
should be considered for all variables which do not need to be
exported.
silence find's stderr
use arithmetic logic for testing UID integer
remove superfluous quoting. eliminate $(cat)