sanitize = function sanitize(message, allowedOrigin) {
    if (typeof allowedOrigin === 'string' && message.origin !== allowedOrigin) return false;
    if (!message.data) return false;
    if (typeof message.data === 'object' && !('postmate' in message.data)) return false;
    if (message.data.type !== messageType) return false;
    if (!messageTypes[message.data.postmate]) return false;
    return true;
  }
Ensures that a message is safe to interpret
@param  {Object} message The postmate message being sent
@param  {String|Boolean} allowedOrigin The whitelisted origin or false to skip origin check
@return {Boolean}