Add explicit .json extension in require

Closes GH-10.
Related to GH-8.
Related to GH-3.
Related to GH-1.

Author: s1n

lib/index.js

@@ -2,7 +2,7 @@
 
 /* Dependencies. */
 var xtend = require('xtend');
-var defaults = require('./github');
+var defaults = require('./github.json');
 
 /* Expose. */
 module.exports = wrapper;