Remove blocknotify

We used it in early days of development to trigger blocktemplate
changes. We don't need it anymore.

Refactor cli and node into lib and bin targets

This lets us build hydrapool using the same components

Improve best ever difficulty in user dashboard

Add README for stratum crate

Send result/error as null if not present

This conforms our responses to json 1.0 and bitaxe esp miners need this.

prerelease 0.1.0