replace matplotlib loss plot

[bodokaiser]

I am not 100% sure about this one. If we can simplify the remaining matplotlib code after #19 with something very simple (e.g. plt.ion(); plt.plot(test_losses, train_losses)) we might keep this. Alternatively we would write losses to a file and render it in index.html however this may be ugly on its own as we would write quite a bit of javascript.

[bodokaiser]

More ideas on plotting in index.html

• papaparse to read loss.csv which gets appended by main.py
• chartjs to plot data

I will try to implement this first with plain javascript as webpack would add a lot of complexity.