Update to eslint 4

[jannyHou]

Description:

The eslint in this repo is too old and causes lots of conflict when coding in es6 style, http://loopback.io/doc/en/contrib/style-guide.html

Upgrade to

"eslint": "^4.13.1",
"eslint-config-loopback": "^10.0.0",

And get CI pass.

[dhmlau]

with the current version of eslint, is the CI failing?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been closed due to continued inactivity. Thank you for your understanding. If you believe this to be in error, please contact one of the code owners, listed in the CODEOWNERS file at the top-level of this repository.