Based on https://github.com/prettier/prettier/pull/2676
* Thread `path` and `options` through helpers so we don't need to add `needsParens` onto the AST node anymore (mutation)
* Pull test call detection logic out into helper method so it can be re-used for arrow function parens
* Add arrow function parens option implementation (avoid/always)
* Don't break arrow function parens around (done) in test call
* Verify parsers against same snapshot
- Reworked run_spec, now accepts 3th optional array argument for
additional parsers to verify against
- Merged duplicate run_spec configs
- Removed duplicate snapshot data
* Formatted run_spec.js with prettier
* Fixed node4 incompatibility
Lucas Duailibe