Update README.md

Generally made the readme a bit more verbose and informative while hopefully conserving the funny bits.

I removed the link to Wikipedia referencing the Dogecoin block rewards and included both the old and current block reward scheme in the readme because this is something people expect to find in the primary readme of a project in my opinion (not to mention that Wikipedia should ideally have an authoritative document saying so and which isn't the source code, otherwise this sort of thing tends to happen: https://xkcd.com/978/ ;-))

Just my 2 Doge. :D