_exportData = function ( dt, config )
{
	var newLine = _newLine( config );
	var data = dt.buttons.exportData( config.exportOptions );
	var boundary = config.fieldBoundary;
	var separator = config.fieldSeparator;
	var reBoundary = new RegExp( boundary, 'g' );
	var escapeChar = config.escapeChar !== undefined ?
		config.escapeChar :
		'\\';
	var join = function ( a ) {
		var s = '';

		// If there is a field boundary, then we might need to escape it in
		// the source data
		for ( var i=0, ien=a.length ; i<ien ; i++ ) {
			if ( i > 0 ) {
				s += separator;
			}

			s += boundary ?
				boundary + ('' + a[i]).replace( reBoundary, escapeChar+boundary ) + boundary :
				a[i];
		}

		return s;
	};

	var header = config.header ? join( data.header )+newLine : '';
	var footer = config.footer && data.footer ? newLine+join( data.footer ) : '';
	var body = [];

	for ( var i=0, ien=data.body.length ; i<ien ; i++ ) {
		body.push( join( data.body[i] ) );
	}

	return {
		str: header + body.join( newLine ) + footer,
		rows: body.length
	};
}
Combine the data from the `buttons.exportData` method into a string that
will be used in the export file.

@param  {DataTable.Api} dt     DataTables API instance
@param  {object}        config Button configuration
@return {object}               The data to export