[api] `File.saveSync()` should return store content
[api] `File.saveSync()` should return store content

Fixes #27.

indexzero/nconf,olalonde/nconf,remy/nconf,HansHammel/nconf,Dependencies/nconf,imjerrybao/nconf,NickHeiner/nconf,bryce-gibson/nconf,ChristianMurphy/nconf,philip1986/nconf