Update project README

[lemmih]

Issue summary

The Forest README.md file could be spiced up and made more approachable:

• See https://www.makeareadme.com/ for general techniques.
• See https://github.com/matiassingers/awesome-readme for examples.
• Get rid of the Our crates section. It doesn't matter to much people and it takes up too much space.
• Arrange sections with introductions and beginner information first. We want to tell people what Forest is and how it is used before we go into details about dependencies, installation, testing, etc.
• Show a demo of running forest: (Maybe download a calibnet snapshot), create a wallet, fund the wallet from the calibnet faucet, send the FIL to a separate account. Use https://asciinema.org/.
• Use more emoticons.

Other information and links