Remove fig.packages replace with real deps.

This change will allow users to install the latest `docker-py` which adds `.dockerignore` support.

It is also much easier to manage dependencies with a version, instead of trying to merge in patches from another repo.

If someone needs to run the latest `docker-py` (as I do), pip supports git urls (http://pip.readthedocs.org/en/latest/reference/pip_install.html#git), so you can set a requirement of the master branch. This also lets you run your against your own fork if the upstream is  slow to merge in PRs.

I've verified that `script/build-linux`, and `script/build-osx` still works (as well as the test suite). Let me know if there are any other tests I should run.


Could we add git to the first apt-get install so the caching works right?