create directory & readme file for discovery.js module

[sethvincent]

i think we're going to follow a pattern of each big module in the lib folder living in a directory with a README.md file, so we can start doing that with discovery.js

tasks:

• move lib/discovery.js to lib/discovery/index.js
• decide what these internal readme files should include (basic description, usage example, link to tests, what else?)
• create README.md file with content

[sethvincent]

@achou11 here's what I've got so far for other module readmes in the lib directory: a1be680

Anything else we should have in there?

[achou11]

@achou11 here's what I've got so far for other module readmes in the lib directory: a1be680

Anything else we should have in there?

can't think of anything else beyond what you listed :)