Exposing as a node module.  Adding lib/doxx.js as node "main" file in
package.json.  Moving main application logic from bin/doxx to
lib/doxx.js and bin/doxx calls lib/doxx.js.  Adding lib/defaults.js to
specify default program options (shared by lib/doxx.js and bin/doxx).
Merge pull request #47 from leejt489/master

Exposing as a node module