Ability to specify Host Devices during container start

[dims]

The command line and daemon started supporting --device
parameter during docker start a while ago in the following commit:
moby/moby@e855c4b

Since the command line looks like this,
--device=[] Add a host device to the container (e.g. --device=/dev/sdc:/dev/xvdc)
This patch allows a list of strings to be passed into the start() method
and we parse out the 3 components just like in the above mentioned commit

[shin-]

Looks good, can you

1. Add the missing newline at the end of the utils.py file
2. Add some documentation to the README file explaining what format is expected for the devices param, similar to this section

Thanks!

[dims]

@shin- I've addressed the 2 suggestions, can you please take alook when you get a chance?

[shin-]

Thanks!