Lean geth image

[nimakaviani]

• [x] document your feature
• [x] comment your code
• [x] update the README / how-to-run
• [x] have tests
• [x] get reviews

[cfdreddbot]

:white_check_mark: Hey nimakaviani! The commit authors and yourself have already signed the CLA.

[nimakaviani]

nimak/geth only contains what we build with Dockerfile.geth. The image size is much smaller. This is a well overdue change we intended to make.