Fix the symmetry check file for MacOS
Fix the symmetry check file for MacOS

On MacOS X sed and grep are not in /bin/. I assume they're on 
most people's paths so this won't break it for anyone else.
enochd/RMG-Py,nyee/RMG-Py,faribas/RMG-Py,chatelak/RMG-Py,chatelak/RMG-Py,nyee/RMG-Py,nickvandewiele/RMG-Py,comocheng/RMG-Py,comocheng/RMG-Py,nickvandewiele/RMG-Py,pierrelb/RMG-Py,enochd/RMG-Py,faribas/RMG-Py,KEHANG/RMG-Py,KEHANG/RMG-Py,pierrelb/RMG-Py