Docker-squash

- Project was renamed from `docker-scripts` to `docker-squash`
- The `layers` subcommand was removed. This tool purely focuses on the squashing Docker images.
- Better error handling when executing the tool from CLI

Enhancements
- Performance improvements. As part of 63 we investigated and fixed some performance issues. This makes squashing faster even by 40%. It depends of course on the image, but you can expect pretty big performance improvement in any case.

Enhancements
- Add support for Docker `1.10` or newer which introduces new image format
- The `--from-layer` argument can take now numeric value which specifies how many layers should be squashed.
- Temporary directories are now removed in case of failure, see 44.
- Added `--development`, `-d` switch to enable development mode. Currently this enables full stacktraces and does not remove the temporary directories after failure.

Known issues
- In case you want to squash an image containing missing layers (see `docker history IMAGE_ID` to confirm) most probably you'll need to specify numeric value to the `--from-layer` argument which says how many layer you want to squash. It's impossible to reference a missing layer in other way because these layers do not have populated IDs.
- The `layers` sub-command doesn't work (yet)

- When you squash you can now create both - a tarred image **and** load it into Docker. Available only when running from an API, set the `load_image` to True and specify `output_path` too.
- Other small improvements when using the squash tool from API

- Uses `AutoVersionClient` to not fail when there is a mismatch between version of `docker-py` and the server
- Does not fail with stacktrace when no image is specified
- Version information is now printed on execution

- Make sure we do not include `./` as the prefix for files in the squashed tar, thanks TomasTomecek!
- Squashed layers has now a proper `VERSION` file
- Fixed metadata size parameter