function isIntegerOrNull( value ) {
	return ( isInteger( value ) || isNull( value ) );
}
Tests whether a provided value is an integer or null.

@private
@param {*} value - value to test
@returns {boolean} boolean indicating whether a value is an integer or null

@example
var bool = isIntegerOrNull( 3 );
// returns true

bool = isIntegerOrNull( null );
// returns true

bool = isIntegerOrNull( '3' );
// returns false