Elixir Maps With String/Colon Keys Are Atoms

While running the Elixir 1.6 formatter against Today I Learned, this change caught my eye. The formatter changes maps like this:

%{ "short_name": "TIL" }

To this:

%{ short_name: "TIL" }

This change makes sense because "short_name": is just another way to use short_name as an atom key:

iex> %{"key": "value"}
%{key: "value"}

Elixir 1.6's formatter requires this more explicit syntax.