* 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