updated readme with explanations of technologies

I don't agree with the first part; nothing about the Bridge Troll codebase requires you to write in a 'test-first' manner, and tests aren't "so people understand mistakes are a part of the development process", they're to verify that the code you check in doesn't have mistakes. If we have to keep a short description of what tests **are**, that's fine, but I would try to keep specific methodology out of it.