function headercase( str ) {
	str = replace( str, RE_SPECIAL, ' ' );
	str = replace( str, RE_CAMEL, '$1 $2' );
	str = trim( str );
	str = lowercase( str );
	str = startcase( str );
	return replace( str, RE_WHITESPACE, '-' );
}
Converts a string to HTTP header case.

@param {string} str - string to convert
@returns {string} HTTP header-cased string

@example
var out = headercase( 'foo bar' );
// returns 'Foo-Bar'

@example
var out = headercase( 'IS_MOBILE' );
// returns 'Is-Mobile'

@example
var out = headercase( 'Hello World!' );
// returns 'Hello-World'

@example
var out = headercase( '--foo-bar--' );
// returns 'Foo-Bar'