pull in external docs

right now all of the docs are scattered amongst sub-repos, and our main repo just links to them. this is really really shitty and makes it difficult to know where to file issues and difficult to find documentation.

repos that need to be pulled in:

• vinyl-fs (for .src, .dest, and .symlink)
  • vinyl (for what files coming out of .src and .dest look like)
  • glob-stream (for .src)
• chokidar (for .watch)
• undertaker