`Need an atomic-lens for dereferencing and updating atoms.

Need to think deeply about lswap! as well. Thinking this is bogus.

Or not. 😄

Perhaps we just need more functions, like (areset! lens atom value)

Reworked the dewdrop api. Now just need to update the demo.

[ANN] aautil 0.0.3 released with dewdrop. See demo: https://github.com/aatree/aademos/tree/master/lens