feat(block-until-url): Import block-until-url from etcd ebuild.

Cleaned up a bit still the same little script.
feat(update-ssh-keys): Add update-ssh-keys script.

This will replace the current method of appending to
core/.ssh/authorized_keys on every boot in oem scripts or coreos-c10n.

Carefully managing keys and not appending forever seems more
responsible. :)
feat(tests): Start unit testing these scripts!

So much shell goo everywhere, it is high time some of it was tested. :)
feat(tests): Add support for running tests with Travis
feat(resize_state): Rework and add tests to resize_state.

The main changes to the existing resize_state script are for fetching
data from udev instead of parsing and gluing together strings. This
makes the script much more generic and now works with loop devices.

The test script is a little crude and needs to run as root since it
needs to call losetup but it does the job.
add(Makefile): Install via 'make install' to simplify ebuild.

Just to avoid excessive editing of things in different repos.
fix(coreos-startup): Add tmp.mount dependency

Depend on mounting /tmp as tmpfs (unit included with systemd).
feat(virtfs): Add udev rule and systemd service to automount virtfs

This will allow us to provide metadata when running under qemu as an
alternative to ec2-style metadata via a special route and HTTP server
which is the only thing we support right now.
add(coreos-c10n): Moved from etcd, unchanged.

c10n was partially broken when etcd switched to running as its own user
because this script couldn't write user ssh keys any more. Since c10n's
scope is beyond just bootstrapping etcd it needs to live elsewhere
anyway. Will add tests and extend to work with non-ec2 setups soon.
feat(Makefile): Add simple test runner to Makefile

The ebuild can use this to run the python based tests :) Also explicitly
use python2.7 as it is the only version these have been tested on and
likely don't work on other versions.
add(coreos-detect-virt): Move from oem-service since c10n depends on it.
fix(systemd): Various cleanups/fixes for systemd units.

- Add condition to local-enable.service so it doesn't trigger when the
  units directory does not exist or is empty.
- Remove init-state.service, it was just there to create mount points
  but systemd does this automatically.
- Cleanup dependency definitions, systemd automatically creates
  dependencies between mount points so the few explicit ones can go.
- Remove use of local-fs-pre.target sync point, the only relationship we
  need is to only mount state after resizing it. All other mount points
  don't need to pay attention to it.
add(addon*): Generic addon run/config services, replaces oem-service.

So far this does the following:
 If <mountpoint>/run (or run.sh) exists, run it.
 If <mountpoint>/authoized_keys exists, add it to the core user.

This same logic is used for both oem and virtfs mounts.
fix(test_resize_state.sh): Correct small typo
Merge pull request #9 from marineam/virtfs

Virtfs and assorted cleanups etc etc