Membership Plugin: not specified charset_collation in `CREATE TABLE` queries.

Hello there,

Having Membership on a localhost enviroment for testing revealed that charset in not set when creating plugin's tables. My mySQL is apparently falling back to latin_swedish_cias default. All that caused my cyrillic inputs transformed into ????? characters. An easy fix is to rely on $wpdb->charset and $wpdb->collate to make sure all stored data is utf8_general_ci encoded.

Example from upgrade.php:

global $wpdb;

	$charset_collate = '';

	if ( ! empty($wpdb->charset) )
		$charset_collate = "DEFAULT CHARACTER SET $wpdb->charset";
	if ( ! empty($wpdb->collate) )
		$charset_collate .= " COLLATE $wpdb->collate";

	$sql = "CREATE TABLE IF NOT EXISTS " . membership_db_prefix($wpdb, 'pings') . " (
	  	id bigint(20) NOT NULL auto_increment,
		pingname varchar(250) default NULL,
		pinginfo text,
		pingtype varchar(10) default NULL,
	) $charset_collate;";