Fixed a typo in the header of the notebooks.

...es_pyYggdrasil/notebooks/1_0_pyYggdrasilDemo_Basics.ipynb

...yYggdrasil/notebooks/1_1_pyYggdrasilDemo_conditions.ipynb

...rasil/notebooks/3_1_pyYggdrasilDemo_samplesAndCubes.ipynb

...l/notebooks/5_0_pyYggdrasilDemo_randomDistributions.ipynb

...Yggdrasil/notebooks/7_0_pyYggdrasilDemo_treeFitting.ipynb

...gdrasil/notebooks/7_1_pyYggdrasilDemo_treeFitting_2.ipynb

...drasil/notebooks/7_2_pyYggdrasilDemo_inspectingTree.ipynb

...Yggdrasil/notebooks/7_3_pyYggdrasilDemo_treeSampler.ipynb

...ggdrasil/notebooks/pyYggdrasilDemo_for_presentation.ipynb