Google, the company with perhaps the greatest artificial intelligence chops and the biggest collection of data about you — both of which power effective bots — has been behind here. But it is almost certainly plotting ways to catch up. Google Now, its personal assistant system built within Android, serves many functions of the new wave of bots, but has had hiccups. The company is reportedly working on a chatbot that will live in a mobile messaging product and is experimenting with ways to integrate Now deeper with search.
Chatfuel is a platform that lets you build your own Chatbot for Messenger (and Telegram) for free. The only limit is if you pass more than 100,000 conversations per month, but for most businesses that won't be an issue. No understanding of code is required and it has a simple drag-and-drop interface. Think Wix/Squarespace for bots (side note: I have zero affiliation with Chatfuel).