first trial of extraction
added get_science_slice and moved extraction
Extraction using more pre-defined values
Rename output spectrum columns
added default_trace_position to slice object
added mask to gmos __init__. added comments to GMOSMask to explain the decoupling to a file
fixed up the longslit_problem. the science_frames seem to work.
added the docs and am playing with the science_sets.
slowly building documentation - including rtd requirements file