all: migrate to github.com/inconshreveable/log15
Created by: keegancsmith
We currently use gopkg.in/inconshreveable/log15.v2, which points to github.com/inconshreveable/log15. However, recently goimports started inserting github.com domain instead of the gopkg.in domain. This also seems to be the prefered import path based on the documentation / import paths in the log15.