ignore ls aliasing in fry-ls

I added `env` to the ls line after realizing that I had aliased `ls` to `ls -AFC` which prints color control characters even to a non-tty, preventing fry-ls from finding ruby versions by string match.
switching to use of `command` instead of `env` to make it more fishy
Merge pull request #8 from mrak/patch-1

ignore ls aliasing in fry-ls