Creating a re-attachment and promotion service in IOTA Go

[jakubcech]

Description

A full walk through on how to create a re-attachment and promotion service using the GO Client library.

If you implement this in one library language, please post the results in the other tasks so that others can follow the same approach.

[JakeSCahill]

JavaScript guide here for future reference: https://github.com/iotaledger/documentation/blob/develop/client-libraries/0.1/how-to-guides/js/confirm-pending-bundle.md