Add fileio.is_block and fix size calcs

Don't just return 0 for size if a blockdev, use get_disk_size to get it.

get_disk_size returns sectors, make sure to multiply by sectorsize.

Add is_block property to fileiostorageobject

Signed-off-by: Andy Grover <agrover@redhat.com>
Rename README to READM.md and update for new project info

Signed-off-by: Andy Grover <agrover@redhat.com>