WIP: initial ci config

.gitlab-ci.yml

Dockerfile

ci/install_libsharp.sh

ci/install_pyfftw.sh

ci/requirements.txt

ci/requirements_base.txt

nifty/__init__.py

test/hdf5_init_test.hdf5

test/hdf5_test_folder/hdf5_init_test.hdf5

test/hdf5_test_folder/hdf5_init_test_2.hdf5

test/test_nifty.py

test/test_nifty_field.py

test/test_nifty_operators.py

test/test_nifty_spaces.py

test/test_nifty_transforms.py

test/test_nifty_utilities.py

test/test_trivial.py