Get the Mergeable status of the PR before updating the
Status. This allows for the Status to be a required
Status for merging the PR. This allows us to use the
atlantis status as a Required status, which is the
configuration often used, since most deployments
want to ensure tf plans have all been successfully
applied before merging
Issue: https://github.com/runatlantis/atlantis/issues/453
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.