Unify code style using Prettier and updates ESLint rules

[kamilogorek]

This PR includes:

• unified package.json file, so it's almost exactly the same as raven-node one (missing author field)
• prettier setup with husky, so it runs for every file that's about to be commited
• updated grunt-eslint, which allows us to use eslint-disable-next-line clause (prettier moves eslint-disable-line clauses to the line below, which breaks it's functionality)
• used prettier options from sentry repository and extended eslint config to use eslint-config-prettier. This way prettier won't collide with any stylistic rules of eslint.
• added lint script to package.json

Notes:

• no manual code changes has been made in this PR
• setup and config has been done in a separate commit, and automated changes has been made in separate ones
• all tests are passing

Related raven-node PR: getsentry/raven-node#364

[HazAT]

I just want to point out the parameters we use for sentry itself.
https://github.com/getsentry/sentry/blob/master/src/sentry/lint/engine.py#L184-L190
We probably don't need the jsx option but we should at least consider having the same options for all ours repos.

[HazAT]

But other than that, nice job 👍

[kamilogorek]

Agree. We should also consider removing ESLint rules that are touching anything related to code style, as they might clash with Prettier. For example by using https://github.com/prettier/eslint-config-prettier

[kamilogorek]

@HazAT all updated. Same changes are reflected in getsentry/raven-node#364

used prettier options from sentry repository and extended eslint config to use eslint-config-prettier. This way prettier won't collide with any stylistic rules of eslint, see fe8a6fb. Those rules were found using their CLI https://github.com/prettier/eslint-config-prettier#cli-helper-tool

[benvinegar]

😱