Updates to readme and cosmetic changes to figures

[bazzilic]

1) Some parts of our existing readme were quite outdated 2) Two illustrations we had in the readme were more or less the same illustration, so I only left one 3) Since there are time after time attempts to mock Taiga out, and there is rising interest in Taiga from the outside, I think it's appropriate to give a super condensed crash course on Taiga in the README 4) Added an example of a basic transaction in the end, will add some more in the future

[bazzilic]

I think I addressed most of the comments.