Proxy list does not contain release tag v2.0.0

[erleene]

We'd like to have the ability to always download the latest released tag version of the master branch, therefore we need the proxy list to be always updated with the newest release tag.

This will give the ability to configure the provider object within the osprey Config object.

Currently when we try to update our dependencies with go get -t github.com/sky-uk/osprey, it ends up pulling the v1.5.0, but we have checked that the latest release tag is v2.0.0 from the master branch. However, this isn't in the proxy list below:
https://proxy.golang.org/github.com/sky-uk/osprey/@v/list

[totahuanocotl]

Thanks for pointing this out @erleene!