add memory and cpu shares support

@ibuildthecloud  @cjellick  added support to cattle for memory and CPUshares . 
Same comment as above just make these more readable.
```python
assert actual_devices[0]['CgroupPermissions'] == 'rw'
assert actual_devices[0]['PathOnHost'] == '/dev/null'
assert actual_devices[0]['PathInContainer'] == '/dev/xnull'
```