Rewrite README completely
Rewrite README completely

I improved the structure of the text by dividing everything into sections.
Old dependencies have been updated to more relevant versions.
Some sections that are documented elsewhere, e.g. `signalflow` in the wiki,
have been removed in favor of a link.

nidrosianDeath/matlab2tikz,miscco/matlab2tikz,matlab2tikz/matlab2tikz,egeerardyn/matlab2tikz,LJeub/matlab2tikz,PeterPablo/matlab2tikz,RPeschke/matlab2tikz,matlab2tikz/matlab2tikz,egeerardyn/matlab2tikz