Add auth and a function to sync a design doc.

With environment variables COUCHDB_USERNAME and COUCHDB_PASSWORD defined, will
connect as that user.

Now uses COUCHDB_PORT if defined.

Add a function to save a design document defined as a YAML file. Why YAML?
Because it's very easy to add Javascript code with syntax highlighting. Plus,
the general format is even lighter than other format like JSON.
Merge pull request #2 from ooda/improve-couchdb

Add auth and a function to sync a design doc.