Update README

[karbassi]

The README is lacking a few things...

• Convert to Markdown.
• Add Logo.
• Add image/gif of it running in terminal.
• Update travis-ci badge.
• Add installation instructions for OS X/MacOS, Windows, and Linux
• Add Code of Conduct link. (via Create a Code of Conduct #216)
• Add Contributing link. (via Updated CONTRIBUTING.md #210)
• Add Changelog link. (via Move over Changelog from wiki to github and changelog.md #209)