Suggestion: Add a .text method for plain text tooltips

Sometimes you just want to display plain text in your tooltips, and doing so requires that you first escape your text before you use it for `.html()`. If you forget, you can introduce XSS security issues. It would be nice if there was a `.text()` method you could use instead, so you don't have to worry about escaping text yourself. This would be similar to `.text()` in JQuery.