update deprecated code to make it work with elixir 0.13

[michelson]

Hi , this pull request is made in order to make this library compile with elixir 0.13

regards

[mweibel]

👍

In order to make it compile on elixir 0.14.1, I updated the exceptions.ex file as follows:

diff --git a/lib/data/exceptions.ex b/lib/data/exceptions.ex
index 23521f1..c70816a 100644
--- a/lib/data/exceptions.ex
+++ b/lib/data/exceptions.ex
@@ -6,15 +6,21 @@
 #
 #  0. You just DO WHAT THE FUCK YOU WANT TO.

-defexception Data.Empty, message: "the data is empty"
-defexception Data.OutOfBounds, message: "out of bounds"
+defmodule Data.Empty do
+  defexception message: "the data is empty"
+end
+defmodule Data.OutOfBounds do
+  defexception message: "out of bounds"
+end
+
+defmodule Data.Missing do
+  defexception message: nil

-defexception Data.Missing, key: nil, what: nil do
-  def message( key ) when key != nil do
+  def exception(key: key) when key != nil do
     "key missing: #{inspect key}"
   end

-  def message( what ) when what != nil do
+  def exception(what: what) when what != nil do
     "#{inspect what} is missing"
   end
 end

I didn't test that out yet however, might be wrong ;)