Data coersion

[iamvery]

All the examples given of ratchet show raw data as a static map. This is not realistic. We need to provide some functionality that helps map user's data into the form ratchet expects...

[iamvery]

This is probably addressed by #46. It's not really a lot of functionality, but the basic idea is:

Data.new
|> Data.scope(:foo, "bar")
# => %{foo: "bar"}

It would be interesting to see if a macro could be developed to save the Map functions called at runtime.