Add README pointing to go bindings repo

Instead of adding the code for the go bindings to this repository it is
favourable to put them in their own dedicated repo. This is more compatible
with golang's dependency resolution mechanism.
I think that adding a README pointing to where the go bindings can be found
is a good way to keep an overview of all available bindings in the main repo.
Merge pull request #79 from mkilling/goejdb-reference

Add README pointing to go bindings repo