ci: remove greenkeeper lockfile upload step

[ChristianMurphy]

The GreenKeeper lockfile upload step, requires having a secure token injected into the public continuous integration environment.
With the current GitHub oauth API, this would mean the generating user would need to create a token, that gives write access to ALL of their public GitHub repositories.
This might be feasible with a build user scoped to a single repository, or if GitHub improves their API.
However at the moment this seems like a security risk.

Short term the best solution appears to be disabling the upload step, so CI doesn't waste time attempting a push that will not work.
Leaving humans to manually rm -rf package-lock.json node_modules && npm install && git commit -a -m "chore(package): update package lock file" && git push upstream

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[apetro]

Is there documentation to update to note when and how what humans ought to

rm -rf package-lock.json node_modules && npm install && git commit -a -m "chore(package): update package lock file" && git push upstream"

[ChristianMurphy]

@apetro if this moves forward, absolutely!
I'm currently digging more into secure storage of tokens on CI, and limiting scope of tokens.
Ideally, I'd like greenkeeper-lockfile-upload to run, and potentially would be interested in investigating using semantic-release.

[ChristianMurphy]

With the plan for #726, there will be a need for a secure way for CI to push to master.
After some additional research it looks like deployment keys could be a good approach.