chore(ci): use npm to install greenkeeper-lockfile for now
chore(ci): use npm to install greenkeeper-lockfile for now

https://github.com/greenkeeperio/greenkeeper-lockfile/issues/98

alangpierce/decaffeinate,eventualbuddha/decaffeinate,decaffeinate/decaffeinate,eventualbuddha/decaffeinate,alangpierce/decaffeinate,alangpierce/decaffeinate,decaffeinate/decaffeinate