Tests for notebooks

[aloukina]

Even though our initial intent was not to have much code in the notebooks beyond reading in .csv and displaying tables, the code for plots etc. is becoming increasingly complex (cf. conditions for piechart generation). We might consider taking those out into a module and writing unit tests.

[alex-treebeard]

Hi @aloukina , if you are still interested in this I've just released nbmake and nbmake-action