Move code from lessons to notebooks

[seidlr]

• I've moved the code from lesson4.py and lesson5.py into Jupyter notebooks. Now, the pitch plots can be investigated directly on github.
• I've updated the readme to link to each lesson notebook and allow to run them on binder without installation
• I've added an environment.yml file for an easy installation of the dependencies using conda.
• I've added a .gitignore file.

I haven't touched any code, therefore it should be okay to merge without any conflicts.

[malo4]

@seidlr one minor suggestion on Lesson6.ipynb:
You can use %matplotlib notebook (to render interactive plots) before cell 5. In this way, as Laurie does in his video, will be able to see the actual values of the Pitch Control surface as you move your cursor around the field.

[seidlr]

@malo4 Sounds great. I tested it offline in my notebook and I get way too large plots. This might have to do with my setup. I also tested it on Google Colab and here the plots are not shown at all.
Thus, I will keep it this way for the moment even though visually inspecting the pitch control surface would, indeed, be very valuable.

[malo4]

@seidlr Aw, you are right. Seems that there's an issue w/ google colab and interactive plots.
As for the jupyter notebook, %matplotlib notebook used figure.dpi, so to get consistent sizes you'll need something like:
import matplotlib as mpl
mpl.rcParams['savefig.dpi'] = 80
mpl.rcParams['figure.dpi'] = 80
Hope this helps!