fix(coreos-install): Add support for choosing channels, new bucket URLs
fix(coreos-install): Replace partprobe with blockdev.

We don't need the fancier partition scanning logic partprobe defines and
we certainly don't want the warnings it generates in the process. Simply
calling the kernel ioctl to re-read the whole disk's partition table is
sufficient since no partitions on the device should be in use.
fix(coreos-install): Switch from lsblk to blkid and search by LABEL

This fixes compatibility with old versions of util-linux because Ubuntu.
Merge pull request #99 from marineam/buckets

Buckets of fun
fix(coreos-install): Add -C to getopts

Missed this in e21594d1
Merge pull request #100 from marineam/getopts

fix(coreos-install): Add -C to getopts
fix(coreos-install): Add channel to final status message.
fix(motd): use correct CoreOS colours
Merge pull request #102 from jonboulle/master

fix(motd): use correct CoreOS colours
Merge pull request #101 from marineam/channel

fix(coreos-install): Add channel to final status message.
Merge pull request #103 from philips/fix-motd-gen

fix(systemd): add OnBootSec=0 for motdgen.timer