Checks if the given API is an sync function or not.

Example Usage:

 
var anAsync = require('an-async');
var fs = require('fs');
 
console.log(anAsync(fs.stat)) // Logs true.
 
console.log(anAsync(fs.statSync)) // Logs false.

TODO:

• Find a better way rather than the nasty R.E. (maybe sync ro async attributes?)