Add the ability to include yaml tasks from zip files

Zipfiles in python are considered a first class citizen. You can
bundle python scripts into zipfiles and execute them directly.

We use a similar method of deployment based on pants:
https://github.com/twitter/commons

This builds pex files that are basically self contained python
binaries. We need the ability to reference tasks bundled in the
pex files from playbooks external to the pex. This patch set
adds in the ability to do so. It would be fairly trivial to exapnd
it to also support loading directly from tar archives as well.

There should be no impact to any end user with this change.