Improve the organization of the docs -- put important things in README

People are looking for usage docs in the README, and that's where they should be. I've seen too many "I can't run rake convert" questions over and over. This will solve that and help so many people.
Changed heading sizes slightly and added 3.0 blurb

Also added the word "Compass" all over the compass section to reduce confusion for Rails people.
Added Bootstrap 3 note in Development section for users

Again trying to redirect confused people as best as we can.
Merge pull request #436 from thomas-mcdonald/trisweb-update-docs-to-be-clearer

Improve the organization of the docs -- put important things in README