Moved nifty source code into nifty subdirectory.

d2o_config

nifty/__init__.py

nifty/config/__init__.py

nifty/config/d2o_config.py

nifty/config/nifty_about.py

nifty/config/nifty_config.py

nifty/demos/__init__.py

nifty/demos/demo_excaliwir.py

nifty/demos/demo_faraday.py

nifty/demos/demo_faraday_map.npy

nifty/demos/demo_tomography.py

nifty/demos/demo_wf1.py

nifty/demos/demo_wf2.py

nifty/demos/demo_wf3.py

nifty/demos/demos_core.py

nifty/dummys/__init__.py

nifty/dummys/gfft_dummy.py

nifty/field.py

nifty/field_types/__init__.py

nifty/field_types/base_field_type.py