replace os/user with go-homedir

os/user can't be used in cross-platform builds, hence we vendor a
cross-platform hack.

Signed-off-by: Peter Salvatore <peter@psftw.com>
Merge pull request #9 from psftw/host-management

replace os/user with go-homedir
Vendoring Gophercloud for Rackspace host commands.
First cut at a Rackspace host driver.
Allow a manually-specified server name.
Whitespace touchup :lipstick:
List images if --rackspace-image is wrong.
Ditto for flavors.
Image list formatting :lipstick:
CoreOS images use "core", others use "root".

As far as I know, anyway.
Support Ubuntu and CoreOS.