Revert "mcpi -> minecraft" rename for compatibility

I suspect I could use `__init__` magic but I cannot yet work out how
Fix incorrect import
Restore `Minecraft.create()` for backwards-compatibility

Partial revert of 8eec71a9040ece62001a25503404087937fbbb92

While `Minecraft.create()` isn't particularly Pythonic, it's what was
documented in
http://www.stuffaboutcode.com/p/minecraft-api-reference.html and
http://www.raspberrypi.org/documentation/usage/minecraft/ so lets not
break it
Deprecation warning on `Minecraft.create()`