Update README.md

README.md

@@ -17,6 +17,10 @@ data_graphic({
 })
 ```
 
+The API is simple. All that's needed to create a graphic is to specify a few default parameters and then, if desired, override one or more of the [optional parameters on offer](https://github.com/mozilla/metrics-graphics/wiki/List-of-Options). We don't maintain state. To update a graphic, one would call data_graphic on the same target element.
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+The library is data-source agnostic. While it provides a number of convenience functions and options that allow for graphics to better handle things like missing observations, it doesn't care where the data comes from.
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 While we are currently using semantic versioning, you should consider v0.* to have commits that will break things if you are external to Mozilla. This library is in its pre-Cambrian period of wild ideas, and parts of the API will slowly but surely become solidified as we use this more and more internally.
 
 Though originally envisioned for Mozilla Metrics dashboard projects, we are making this repository public for other to use, knowing full well that we are far from having this project in good-enough shape. Take a look at the issues to see the milestones and other upcoming work on this repository. We plan on having fuller documentation in the next milestone, as well as a guide to how to contribute to the library in a way that makes us feel warm inside when we accept your pull request.