This will reduce the bundle size by ~23%(117kb).
Only 4 methods were used `flatten`, `flatMap`, `omitBy`, and `groupBy`.
`omitBy and `groupBy` were recreated while the es2019 implementations of
`flatten` and `flatMap` are used.
`lodash` is still used in the tests which is fine because it makes the
tests cleaner.
Closes#2118
* sets up linting config and runs `yarn lint --fix` once, so that all changes will show up correctly in future PRs.
* Note that there are still a lot of linter errors.
* Add *.tsbuildinfo to .gitignore
* Bump versions of dependencies, nyc and yargs
* Drop support for node 9 (EOL 2018-06-30)
https://github.com/nodejs/Release
* Add getTransaction snippet
