Add Apache 2 license and Hootsuite copyright to all golang
files. Add a disclaimer that the files have been modified
hereafter by contributors to this repo in order to abide
by the Apache 2 license requirements.
Operating on forked pull requests is dangerous if it's a public repo
because anyone can make a pull request to a public repo. We default to
false like CircleCI and TravisCI who don't allow credentials to be
available on fork PRs.
