Better organize package.json

[sampaiodiego]

I've done a few things on this PR:

• Merge eslint and stylelint into lint npm script. This is better IMO because where ever we use lint script (like husky pre-push hook) it will validate both javascript and css.
• Changed to use Meteor's npm instead of installed on host. This will make sure the correct npm version is used to everything
• Removed npm i from start script. This doesn't make sense IMO and was causing changes to package-lock.json everytime start was called.