Many links broken by search/replace

[yupferris]

Looks like in 573b31c, there was a search/replace from "gameboy" to "Game Boy" in README.md, which broke many links, such as Game Boy Demospotting (should be http://gameboy.modermodemet.se/), etc. I don't want to just revert the commit and fix those as it looks like there were a lot of other useful changes in that commit, but it needs to be gone through so these links can be fixed. I suggest the commit author take this task, but I wouldn't mind doing it myself either :)

[avivace]

Woops! Thanks for letting me know. (Almost) every link should be back now.

[yupferris]

Looks like it, nice one :)