Rename package

[sjwiesman]

The current package statefun_go is not idiomatic with its underscore. We should rename it to something else.

I'm not sure if it is alright to have the package structure different from the file structure but the end goal is to donate this codebase to apache/flink-statefun which is a mono-repo containing multiple languages. This means will want some signifier that this package contains the go sdk specifically.

[marcellanz]

One probably would have a separate repository for the go implementation here in the flink project especially which will have a descriptive name state that this is the go sdk of statefun perhaps something like: https://github.com/apache/flink-statefun-go and then having descriptive packages. File directory structure also follow the package structure. More about this can be found here:
https://golang.org/doc/effective_go.html#names
https://blog.golang.org/package-names

[sjwiesman]

Thanks for the resources!

fixed in bdd63ac