Suggestion: linting and flow error checking

This is a:

- [ ] Bug Report
- [ ] Feature Request
- [ ] Question
- [x] Other

Which concerns:

- [x] flow-runtime
- [x] babel-plugin-flow-runtime
- [x] flow-runtime-validators
- [x] flow-runtime-mobx
- [x] flow-config-parser
- [x] The documentation website

### What is the current behaviour?

Currently linting and flow returns a ton of errors. And they are never run on CI.

### What is the expected behaviour?

I expect linting rules and flow to be running on CI.

### Suggestions

Fixing flow errors might be a lot of work, but it would definitely be easier to keep all packages in sync with eslint and flow verision similar to other lerna mono repos.

If you guys would like it I can contribute with the following:
- move eslint to root package (one linting installing)
- fix linting errors
- enforcing linting on CI
- move flow-bin and configuration to root package
- clean up all the flow-typed folders as we only need one

Let me know if you are interested in this.