redismodule.h does not seem up-to date and `example`fails to run with redis `unstable`.

[JoanFM]

Hello team,

Trying to build an example module with the redismodule.hcopied in this repo did not work, but it worked when I took it from the redis main repository.

Perhaps would be better to not have the copy in this repo and just link the users to the proper place?

Thanks