So I found it surprising that while `dragToValue:` takes a float between 0 and 1, `value` returns a string like "100%". I added `floatValue` to allow the slider's value to be queried in a way consistent with `dragToValue:`.

The naming is still pretty confusing, though. Is there a better way?

I could, for example, change `dragToValue` to take a value between 0 and 100 and divide that value before passing it off to UIAutomation, but this differs from the `UISlider` behavior of taking a value between 0 and 1. 

I could also override `value` to return a string between 0 and 1, with no percent sign. It doesn't look like any of the other `SLElement` subclasses change the value that UIAutomation returns, though.