Initial add of conda.yaml file

This pull request addresses the following issue:

"Add conda.yaml file" #159

I'm not sure if this works or if it's exactly what you're looking for, but I don't think I can make any further progress, since I don't know how to test it.
OK, I was just following the example here: http://conda.pydata.org/docs/build.html.  GIT_BUILD_STR combines GIT_DESCRIBE_NUMBER and GIT_DESCRIBE_HASH. If we just want the build number, then I'll remove the build string.