add -path to inventory

My VMware Fusion VM does not create /dev/disk/by-id entries
for mptsas drives. This allows inventory to point at /dev/disk/by-path
which works fine for cases where it's the next-best option.
Clean up argument parsing.

main.go is now only an entry point to the effio package.

Made commands with < 3 args work without bogus filler args.

effio -h / effio help / effio -help are now less malevolent
Add a device file for my VMware instance.

I use 2 virtual drives, one for OS and the other for testing.
The test drive has one whole-disk partition on it.
Add a trivial fio test.
Clean up arg parsing some more.
Rename command files to be consistent.
go fmt
move sysfs helpers to their own file
use template vars in trivial fio test
Add device manifest for MacbookPro10,1 (OSX)