Using defaults, env or argv causes save to fail

[calmh]

Having a .defaults call in the chain causes save to fail with an exception as below. The same happens with either .env or .argv present. The examples seem to indicate this should be a valid way to use nconf.

jb@jborg-mbp:~/tmp % npm list
/Users/jb/tmp
└─┬ nconf@0.5.1 
  ├── async@0.1.22 
  ├── ini@1.0.2 
  ├─┬ optimist@0.3.4 
  │ └── wordwrap@0.0.2 
  └── pkginfo@0.2.3 

jb@jborg-mbp:~/tmp % cat test.js 
var nconf = require('nconf');
nconf.file({ file: 'settings.json' });
nconf.defaults({
    foo: 'bar'
});
nconf.save();
jb@jborg-mbp:~/tmp % node test.js 

/Users/jb/tmp/node_modules/nconf/lib/nconf/common.js:96
    Object.keys(obj).forEach(function (key) {
           ^
TypeError: Object.keys called on non-object
    at Function.keys (native)
    at /Users/jb/tmp/node_modules/nconf/lib/nconf/common.js:96:12
    at Array.forEach (native)
    at Object.merge (/Users/jb/tmp/node_modules/nconf/lib/nconf/common.js:95:8)
    at [object Object].save (/Users/jb/tmp/node_modules/nconf/lib/nconf/provider.js:425:19)
    at Object.<anonymous> (/Users/jb/tmp/test.js:6:7)
    at Module._compile (module.js:446:26)
    at Object..js (module.js:464:10)
    at Module.load (module.js:353:31)
    at Function._load (module.js:311:12)

[pksunkara]

Duplicate of #36