Write a regions notebook in astropy-tutorials

[cdeil]

As suggested by @astrofrog and me at https://github.com/astropy/regions/pull/87#issuecomment-264002104, we should write a "getting started" notebook for regions, and put it in astropy-tutorials.

I think a 5 to 10 min read would be appropriate, and start and end by pointing at the longer Sphinx docs.

I'm putting this under the 0.2 milestone, but this can happen after the release. It should happen before the 0.2 announcement to astropy-dev though, so that this can be mentioned.

Anyone interested to do this?

If no, I'll write it on Monday latest.

[janerigby]

I wrote a tutorial 1 yr ago. Unfortunately, it's not working at the moment: https://github.com/janerigby/NB/blob/master/Example%20pyds9%20and%20pyregion.ipynb

Please see issue 124: https://github.com/astropy/pyregion/issues/124