Dockerfile and some fixes for ECR

Hi,

As I've promised I'm opening a pull request with the rest of my changes, I mean:

1. I've added Dockerfile to build a project into docker image
2. I've changed the logic of parsing repo name - instead of depending on some prefix, now we use full url, that contains region - it is very useful to do that this way, because we have unified way of addressing and also we don't have to have any ~/.aws/config in place to set a region (which is a kind of trouble in docker scenarios)
3. Fixed manifest for destination - ECR requires to set manifest name to be the same as repository name.

The change number 2 is not backward compatible.

I understand that you can reject this PR to be backward compatible and it's ok :)

Best regards

Łukasz Tomaszkiewicz

I've been horrible for not responding faster. How would you feel about taking over the project? I should be able to give you permission to merge and I can give you access to publish on npm too. Would you be interested in that?

I've encountered some issues related to my fixes of manifest - it looks like in some cases docker refuses to use the image as the signature is invalid, unfortunately I haven't figured out the solution yet :( After I resolve the issue I think I can take over the project if you wish :)