Fix readme formatting on pub

[evanweible-wf]

https://pub.dartlang.org/packages/dart_dev

Issues

• GitHub tables are not standard markdown - use HTML tables instead
• Blockquotes end to early..
  • at the beginning rationale
  • under "CLI Usage"
  • under "Programmatic Usage"
• Headers under "Getting Started" are too small
• "Project Configuration" code block is missing most of the code?