Fixing grep in FileFinder to avoid conflicts with colors specified in GREP_OPTIONS

Fixes issues when you have GREP_OPTIONS for grep. Such as:

`GREP_OPTIONS="--color=always";export GREP_OPTIONS`

When you run flog or flay you will get the following error:

`Unknown file type: rb, defaulting to ruby`
`No such file or directory - ./app/controllers/accountants_core/accountants_controller.rb`