Bugfix to make Graudit work on Macs. Currently, the code hardcodes the path /bin/grep in an early test of grep, but correctly uses $BINFILE elsewhere in the code. Under Mac, this is /usr/bin/grep, so on Macs graudit dies silent. This one line fix should address the issue.
Merge pull request #2 from samuelreed/master

Bugfix for making Graudit work on Macs (thanks to @samuelreed)