code: function keyOf(obj, value){
  		for(var key in obj)
  			if(Object.prototype.hasOwnProperty.call(obj, key) && obj[key] === value)
  				return key;
  
  		return null;
  	}
docs: Retrieve object's key paired to given property
  @method keyOf
  @param {Object} obj			Object to get key from
  @param {Mixed} value		Value corresponding to key
  @return {String}			Key or null if no key was found