function isUppercase( value ) {
	return (
		isString( value ) &&
		value === uppercase( value ) &&
		value !== lowercase( value )
	);
}
Tests if a value is an uppercase string.

@param {*} value - value to test
@returns {boolean} boolean indicating whether value is an uppercase string

@example
var bool = isUppercase( 'HELLO' );
// returns true

@example
var bool = isUppercase( 'World' );
// returns false

@example
var bool = isUppercase( '!' );
// returns false

@example
var bool = isUppercase( 'salt and light' );
// returns false