update readme

[fractalbach]

Currently, readme has some random stuff about tile maps.

Should have more info about the game itself and it's current status.

[fractalbach]

"The Game Object" should be updated to show what the IDEAL game APIs should look like.

Atm, it changes too often for it to be worthwhile to keep it updated.

In future, there could be a tool that auto-generates the GitHub markdown, and uses it as a documentation.