Improve README documentation (#467)

We want to provide users with clear documentation on setting up and
using Bamboo. The README does a good job at that task but there are
elements that can be improved to provide greater consistency and more
thorough explanation. This commits aims to improve the README by:

- Changing the organization to include promotional material at the top
  followed by instructions on setup and use.
- Make the promotional material more consistent in language style.
- Expand on the instructions for setup, getting started, and testing.
- Linking to external documentation on every module reference
- Organize links by moving them all to the bottom and establishing more
  consistency in link text