Update docs with how-to guides in addition to quickstart

[lindydonna]

• Document top-level flows like using TypeScript, etc
• Document current config precedence

Joe's feedback in #20:

It seems like we ought to have a new section: "So you've got a Pulumi program, and want to build/deploy it, how do I do that?" Everything is geared towards starting from scratch, so there are steps missing. For instance, it should tell you to yarn install, how to find out what to yarn link, how to know what configuration variables to set, etc.

There are other missing steps. For example, it never tells you how to compile your TypeScript which, though orthogonal to our tool, we should do if we're going to use it in our samples.

The layout of the Quickstart pages are a little confusing, because clicking on the link to Quickstart then puts you on a page with many links, including Overview. Why not just start there automatically.

Let's do one more pass over the Quickstart "as a customer would", after the above changes, and ideally from a clean machine, just to make sure we've ironed out all the kinks.

[lindydonna]

Closing in favor of #73