Move tests folder to top level?

[tsalo]

I think it might be cleaner to have tests at the top level instead of within src/fmripost_template. Not sure if that will work particularly well though.

Here's one organization I think would be nice:

src/
    fmripost_template/
tests/
    data/
    run_local_tests.py
    test_<module1>_<submodule1>.py
    test_<module1>_<submodule2>.py
    test_<module2>_<submodule1>.py
    test_<module2>_<submodule2>.py
    utils.py