Checklist

• I added a descriptive title
• I searched open requests and couldn't find a duplicate

What is the idea?

If I want conda build to output the .conda file format, I current have to set the following in my .condarc:

conda-build:
   pkg_format: 2

On top of that, I think this should be configurable with a command line option.

What should happen?

I really don't like having to specify pkg_format: 2 for the .conda file type in the .condarc file. I think it would make more sense to add something like --pkg-format=conda and have it default --pkg-format=tar.bz2.