Fix vulnerabilities and update other dependencies that don't break tests

[malob]

(Fixes #175)

NPM reports multiple vulnerabilities, and many packages where pretty old in general. Did the following:

• Ran npm audit fix --force, then npm test to ensure all tests still passed (commit 8e97a1d).
• Ran npm up, then npm test to ensure all test still passed (commit c2dd2c8).
• Ran npm outdated and manually updated all packages to latest that didn't break test or change eslint output (commit 5d8f2ce).

Only package that broke tests when manually updated was async. Didn't update eslint related packages since they caused npx eslint . to report errors it wasn't reporting before.

Tested plugin with personal serverless project and everything seems to be working as expected.

[malob]

@pmuens, anything I can do to help get this merge?

[jwkicklighter]

@pmuens What needs to be done to merge this?

[pmuens]

Hey @malob thanks a lot for working on this fix 👍

I just checked out your branch and did a test deployment. Everything works as expected. Will merge this PR and do a new release in the upcoming hour(s).

LGTM