The Vector Calculus tutorial

[francispoulin]

I noticed that the Vector Calculus tutorial has some errors. I am working on fixing them but before I do, I thought I'd ask if someone else might have a working version first?

[francispoulin]

I was able to make some simple changes and am starting to get some plots working. Some issues I have are listed below.

1. I don't know where global_oce_llc90 is to be found exactly. I found the ECCO data for Release 2 and it's mostly working but if someone can point me where to download this specific file, in case it was modified, I am happy to do so. This is important in two lines of the notebook. @ifenty , anything you can help me with here?
2. I am very new to xgcm, which looks great by the way, but for some reasons I am getting all of my plots are flipped left to right. I am including a sample. @rabernat, I realize this isn't your repo but I thought you might know of a quick fix?