Automate conda

Prototype to automate the build of conda packages.

What the script does:
* Downloads iris from github once and/or update it if already exists;
* Gets the version tag from the `setup.py` instead of `git tag`, ensuring that we have the latest information;
* Adds the git release "hash" to the version tag;
* Writes `meta.yaml` inside the chosen `BUILDDIR` using a template where the VERSION string is a place holder;

This workflow will help us to keep track of packages.

TODO:
* Add iris release URL to the meta.yaml;
* Added iris checkout as a git submodel;
* If this works and people accept, propagate this workflow to other packages.