Support multiple creating groups

b = Cgroup::BLKIO.new("hoge")
c = Cgroup::CPU.new("fuga")

p b.exist?
if b.exist?
  p b.throttle_write_bps_device
else
  p "not found groups"
end
b.throttle_write_bps_device = "8:0", "130000000"
p b.throttle_write_bps_device
b.create

p c.exist?
if c.exist?
  p c.shares
else
  p "not found groups"
end
c.shares = 2048
p c.shares
c.create

b.delete
c.delete