Specutils and Specreduce Tutorials

[kelle]

<placeholder issue for links to notebooks @eblur started and our wishlist>

Lots of notes here:
https://docs.google.com/document/d/17m2cRPA8S4Y_kS_CC4P3s08FCaIzNQuUfRruwnsVMvQ/edit#

[kelle]

Adam Burgasser's notebook messing around with Spex data might be a good template for an eventual “plotting” notebook.: https://colab.research.google.com/drive/1eV7-VsHmQQpxgz5pAf8chAvjtme_VRlo

[eblur]

See Issue #440 , #441 , and #438

[eteq]

Some items identified that we would want to be in a specutils tutorial that discusses the "quick plot" functionality:

• Demonstrate the use of a SpectrumCollection and/or a vector Spectrum1D with the plot_quick - if this is awkward we might decide it should instead be in plot_quick (Quick plot method for Spectrum1d specutils#650).
• Demonstrate where to do savefig to demonstrate doing plot_quick and saving it out to a pdf/etc figure - again, if too awkward, we can decide it should be in plot_quick (Quick plot method for Spectrum1d specutils#650).
• Demonstrate adding additional information to the plot - simplest thing here is just ax.set_title, but there's probably more to show like a legend or the like.

Note the above is assuming the plan for the Spectrum1D method that roughly like what's in astropy/specutils#650, which could of course change since the PR isn't yet merged