text: Title: Method to remove InlineKeyboardButton from markup
  Body: As i understand, now InlineKeyboardMarkup is just a dict with lists, so method like pop() will be useful and make code cleaner, at least for newbies like me. 
  For now, to make dynamic inline keyboard with deleting buttons after user clicks on them i need to recreate entire markup from changed list, but it can be simplified by using InlineKeyboardMarkup.pop() or something like that.