Split generation and exportation of image.
Undo some overly aggressive find/replace.
Caller is now responsible for image cleanup.
DRYer
Merge pull request #40 from swipely/decouple_build_and_export

Separate build and export steps available.
Stop building the package twice
Stop putting docker into debian package, todo to add boot.sh
Add a registry to the deb, not a docker
Add experimental TarDiff class
Move auth_config_file to Registry from Docker and remove shell export
TarDiff now accepts a chunk and acts upon the size of the chunk

If not enough of a chunk is given, the method returns false, specifying
it needs more.
If it returns true, then it got a big enough chunk for the header and
the file, and returns true.
Autoload TarDiff, cleanup process and add test script
Swich back to IO based processing, and use IO.pipe
Finish TarDiff for IO formats
Remove test file and lock docker-api to a higher version
Add S3Writer (mimics IO with write and close) and spec
Stop passing the output and input as arguments
Add spec for tar diff
Add tar fixtures for specs
Fixed for the case when the buffer isn't empty before closing