TEST: Move tests into fsl package

MANIFEST.in

fsl/tests/__init__.py

fsl/tests/conftest.py

fsl/tests/test_assertions.py

fsl/tests/test_atlases.py

fsl/tests/test_atlases_query.py

fsl/tests/test_bids.py

fsl/tests/test_bitmap.py

fsl/tests/test_cache.py

fsl/tests/test_cifti.py

fsl/tests/test_deprecated.py

fsl/tests/test_dicom.py

fsl/tests/test_dtifit.py

fsl/tests/test_ensure.py

fsl/tests/test_featanalysis.py

fsl/tests/test_featdesign.py

fsl/tests/test_featimage.py

fsl/tests/test_filetree/__init__.py

fsl/tests/test_filetree/custom.tree

fsl/tests/test_filetree/extract_vars.tree