first attempt at a to_glue machine.  Required fixing some bugs in
__getitem__ but that's no problem
the glue_app becomes part of the cube now so that subsequent calls add
the dataset to an existing session
allow a glue application to be specified.  add docstrings
attempt to accept updates of data collections
have to add cubes to the dataset object, not the datacollection
need to check component labels, not 'components'
autoload glue viewer
add start_gui keyword
fix FITS reading bug
Merge pull request #153 from keflavich/to_glue

Feature request: to_glue
Merge pull request #162 from keflavich/fix_fits

ix FITS reading bug
add a simple to_pvextractor tool
docstring for to_pvextractor
add a quicklook tool for spectra
add quick_look documentation
fix spectral quicklook wcs
Merge pull request #160 from keflavich/to_pvextractor

add `to_pvextractor` tool
add a quicklook tool for spectral slices
fix CASA .image reading: should not assume 3d by default, since usually
stored as 4d
Merge pull request #164 from keflavich/spectral_quicklook

Add a quicklook tool for spectral slices