Test cases

Hi,
I am a bit worried about stability in conda-forge packages.
I suggest that we encourage people to add real test cases such as `make check` or `nosetests` instead of just `command --help` or `test -f /path/to/file` and also take a look at the original package and see how that one is tested through continuous integration if there is any.

Also, I want to add some kind of rule to add test cases for reported issues on feedstocks so that they don't happen again. For example, I had an issue with ffmpeg: https://github.com/conda-forge/ffmpeg-feedstock/issues/2 and I created a pull request: https://github.com/conda-forge/ffmpeg-feedstock/pull/3 both to fix that problem and added a test case so that it doesn't happen again. This should be norm IMHO.

Another example is this issue: https://github.com/conda-forge/hdf5-feedstock/issues/4 while it is fixed now but no test case is added to make sure it doesn't happen again.